There's no such thing as a "bad team" (unless it's genuinely bad, like consisting of Kakunas and Spewpas). Assuming that Aya is no longer travelling with you, you can't just grind in Route 3. That leaves Agate Circus as your primary place for EXP (although the clown can be a real jerk sometimes).
Do you have the TM 18 - Rain Dance? If so, teach it to your Crobat, it has the potential to go outspeed Charlotte's most, if not all of her, Pokemon. Not only does Rain Dance weaken her Pokemon and the field effect, it will boost your Floatzel's Water-type moves and it's Speed, should it have Swift Swim ability.
If your Gardevoir has Trace ability, you might be able to trace Flash Fire, which not only makes it immune to Fire-type moves, but if Gardevoir now gets targeted by one, its Sp. Attack increases.
Then there are the Pokemon with Thick Fat ability, such as Walrein and Snorlax. You can catch Sealeo, which evolves to Walrein, in Ametrine Mountain. Getting Snorlax is a bit more tricky, since you need to have a Whiscash for the trade. You receive Munchlax, who evolves via max happiness.
If you're short on resources and cash, then it might be a tad more difficult to manage. I can't stop you from starting a new game but I wouldn't give up just yet.