All Pokemon evolve from Basics so this helps everyone... early game. I don't see how this is biased towards EXs.
EX Pokemon either stay basic the entire game, or mega evolve and gain access to mega turbo acceleration regardless. Basic Pokemon that evolve into useful stage 1, stage 2 or BREAK Pokemon only have access to this Max Elixer while they are in a form that is overall a burden to the strength of stage 2 and break decks. If basic Pokemon overall were better than it would be less of an issue, but basic Pokemon that can evolve tend to be awful, and so you spend your time either accelerating energy to them to not be used until they evolve, leaving them a huge reliability, or just evolving them straight away but losing out of fast, reliable energy accel that they need to keep up with low cost EX attackers and now even higher cost EX attacks thanks to this card.
Maybe Golduck BREAK and Regirock-AT may be useful in allowing Max Elixer to remain helpful for stage 1, stage 2 and BREAK decks along with EX's, since you would need to accelerate the energy onto Regirock since he is completely protected from trainer cards, and then move the energy to the actual attackers once they evolve and become contenders against the ever more powerful EX Pokemon. Golduck BREAK + Regirock-AT is a lot of cards and a lot of clunk that multi-evolution stage decks can't afford to include either.
In short, this card helps EXs significantly more than it helps other basic Pokemon.