As I see this topic is already full of opinions posted from the point of view of average Pokemon games fans, I shall provide an opinion from a different point of view: that of a writer (because yes, I fancy myself to be a pretty good writer. I actually suck, but that's another story). Therefore, the comments you are about to read do NOT take into consideration the standard instances of the average player (as in, "I hate how in main games the teams that are supposed to be serious menaces usually use horridly weak Pokemon" and stuff like that), instead I will focus my reasoning exclusively on the narration aspect: in other words, I will analyze how effective the villainous team is in telling a story. Please do keep this in mind while reading.
So, traditionally Pokemon games have been plagued by a lack of credible villains: in the first two generations, Team Rocket was infamous not only for the weakness of their Pokemon (which is an aspect that, I repeat, I am not going to take into consideration), but for the even more glaring weakness of its motives, which made their plot very difficult to buy in. Team Rocket wanted to steal Pokemon and sell them on the black market... In a world where a 10 YO kid can just grab a Pokeball and start catching Pokemon to his/her heart content, INCLUDING LEGENDARIES. This, along with the fact that legendaries themselves didn't play any relevant part in the story, made the plot of those games really really weak, but then again, that was mostly due to the fact that the plot wasn't very important to begin with back then, and it took a back seat compared to, well, "gotta catch them all!".
Generation 3 marked the first attempt by Game Freak to give us villains that could be a major driving force in the plot, and that could be seen by players as genuinely heinous: enter Maxie and Archie, whose goal is to cause atrocious cataclysms to expand either the landmass or the sea... Why? Once again, the well-intentioned creators failed at giving us credible motives for the villains' actions, handwaving it all with a generic "I thought expanding the landmass/sea would benefit people". The premises were there, for once a story was actually being told... But then it fell flat, also because of the very simplicistic ending: "oh, a 10 YO kid saved the world by stopping the rampaging legends? Ok then, in such a case everything is fine! Maxie, Archie, you are forgiven! And you, kid hero, come challenge the Pokemon League!".
A villainous team with an organic plan and a clear goal finally debuted in Generation 4: unfortunately, the goal itself was a rather cliché one. However, for the first time we were given a game in which the actions of the villains were the main driving force of the plot, even if most people tend to forget that because the cronic problems (absurdly weak teams for the baddies, the whole plot pretty much forgotten after the final showdown, with the player focusing once again on beating the Pokemon League as if nothing had happened) were still there.
Generation 5 FINALLY gave us a plot that stays relevant from the beginning to the end, and a villain with a very credible goal and a very well tought plan. Sadly, B2/W2 were kinda a step back on this regard (as the aforementioned goal of the Big Bad went from a clever play on the mentality of Pokemon in general, to the generic "I am gonna destroy Unova for revenge, stop me if you can") when compared to B/W, but still, we can say Generation 5 was the first Pokemon game that was 100% succesful in telling a story: however, such success was a rather Phyrric victory, as Generation 6 brought us back to the usual format of villains having a generic goal and being pretty much forgotten after their plot is over, with the player going back to focus on the Pokemon League (at least there were two clever twists in the people for once ACKNOWLEDGING you as a hero, and one of the E4 being a member of the villainous team, even if this particular was rather downplayed and can be seen as one of the MANY plot holes that characterize X/Y).
So, what am I trying to demonstrate with this reasoning of mine? I am trying to demonstrate that, Generation 5 aside, the Pokemon franchise has displayed a glaring lack of truly believable villains (and strong plots built around them) over the years. Because of this, many long-time fans of the series (such as myself) craved a more adult plot, with a more serious villainous team that could be a credible menace for the protagonist and the entire society... And when Pokemon Reborn came 'round and gave us just that, we rejoiced. However, the understandable enthusiasm has caused many players to overlook some flaws that Team Meteor still has.
Namely, it's one flaw: the fear of repeating Game Freak's mistake, which leads to repeated exaggerations in the opposite direction. It's as if Ame (or whoever helps her with the plot) was hell bent into clogging the events with a limitless stream of heinous acts, with no apparent reason other that "I wouldn't want people to think Reborn is NOT darker and edgier!". I mean ok, in order to make a plot darker, you need eviler baddies. But some instances are really gratuitous, and without them the plot could have worked out just as well: for example, the mook horror show we get when storming the Giant Steelix base, with the Meteor Grunt we have come to know by name describing Saphira's attack on the Meteor main force, with A LOT of insistence on how many grunts died, didn't really serve any purpose other than reassuring the player that yes, Reborn is indeed darker and edgier, so don't worry, you are going to get your share of violence in this episode too. Of course, this is part of a general tendency in the whole game to sacrifice realism/credibility/friggin' common sense just for the sake of adding details that can make the plot darker (what with the line-up of the Gym Leaders, which are in theory a group of individuals that, in the Pokemon universe, share a rather important role for the whole society, including in its Reborn incarnation some kids who are locked up in an orphanage AND ABUSED BY THE HEAD OF THE STRUCTURE, and even a ghost), but still, if Team Meteor has a flaw, it is this: main series villainous teams are not credible because they are not dark and evil enough, Team Meteor sometimes exaggerates in the other direction.
It is a honest mistake made with a precise plan in mind, and Ame (or whoever helps her with the plot) had the merit of properly addressing all the situation caused by this extreme "darkness and edginess", without leaving any plot holes... But still, I had to point it out: is Team Meteor a great villainous team? Yes it is. Is it better than the vast majority of main games baddies? Sure it is. But is it flawless? Hell no. In a way, I find B/W to actually be darker than Reborn, the same way Sonic Adventure 2 is darker than Shadow the Hedgehog: sure, the latter has murders and abuses on minors, but the former deconstructs the basic thematics of the franchise in a very clever way. And sometimes, a clever deconstruction does more than a hundred killings for a plot.
tl;dr: praising what's good is fine, but pointing out what isn't is important too, because it sparks a discussion that leads to improvement. Don't let the understandable enthusiasm blind you