Let me bring up two situations both which involve a man who can easily beat a woman in a fight: The first scenario is that the woman is given a knife while the other she's given a Gatling gun. Are either of these fair? No, but only in one does the man really stand a chance to win. Which one do you think best represents the player in terms of Pokemon RPGs. If you guessed woman with a Gatling gun, you are right. So before you spit off about the game being unfair, take a moment to think about that...deeply. Of course the leaders and bosses are stronger than you when you play on equal terms, but it's really up to the player whether they make use of the Gatling gun or the Knife. The knife is easier to wield and takes less time and effort which is often the path most of the players on here take. I don't feel like explaining it all as I've done numerous times in the past. This is just to answer if the game is fair or not.
Now let's break down the one of two core issues the OP is complaining about. The first is the well known exp drought. It's an issue due to a limited amount of trainers giving decent exp where the dilemma is now spending repeated times going through a boss or wasting time doing tedious and extra work on wild Pokemon/rematch trainers to get through said boss. It doesn't help that the higher the levels get, the more difficult it is to keep a steady level curve since you need about all trainers to have 5-6 mons to hit roughly five levels an episode levels 75 and up. The OP hasn't reached that far and hasn't even hit the first true exp drought. This is an issue and it also leads to the second issue of what's going on, but that one applies to Pokemon in general.
The bigger issue is the team that they are using. Most of those Pokemon you get very early on and even for myself I used mostly mons from the early game like Roserade, Gardevoir (before it got the double push back), Lanturn (before it got pushed back), Flygon (when it was Onyx Arcade), Gengar (when it was Wasteland), and Metagross (back when it was available pre-Luna)...I swear that isn't intentional. Point is that you don't really want to change mons due to the dilemma above. The level limiter system (see Rejuvenation) seems to help against this due to the dilemma being significantly less of an issue. I have doubts the OP is as much of an RPG players as they make out to be as this exp system is a well-known, but archaic system due to the sheer amount of time to gain levels. It's unfortunate and we all kind of have our hands tied as no matter how anyone tries to go about it, there will be a very large group pissed off by those decisions.
Now I'm not trying to toot anyone's horn nor berate the work of anyone else's, but I do not think having the Insurgence team work on Reborn would fix the issues, but would actually make the game significantly worse. Ame has some decent idea how to deal with the lategame which I disagree with, but we have a good chunk of people who are capable of doing all the things Insurgence did if not better. Except the customization characters mostly because I ain't dealing with figuring that out (outfits are a different story). There's a mod that lets you used your cursor as a control for bloody sakes. We have at least 6 people around capable of doing quite a lot, myself included. And wouldn't it be easier to work with someone who has been around the community for a while over a whole different group of random guys in a different fandom? You might want to look in that mod market before saying anything else though. You might resolve your own complaints there.