I don't think rotation will help that any. We would still have cards like Hisuian Basculin, Miraidon ex especially, and bombirdier Ex.It just feels useless to repeat the same mantra over and over again. The format is centered around a few extremely broken cards that give decks instant access to every resource (or a collection of these cards, such is the case with Miriadon). Their plans are extremely similar, which is to get their set-up and power up their beatstick of choice. Ironically, since these decks are so ridiculously fast and consistent, whiffing even a piece of your set-up results in a complete one-sided wipeout, which happened in multiple finals of high-profile tournaments.
I don't think it's specifically the "fault" of small Gardevoir, but rather its toxic interaction with Gardevoir ex giving you infinite free energy. The point still stands - to be a successful single-prizer, you need to feature some kind of gimmick or glasscannon free attacks. The design space couldn't be any smaller without eliminating that 90% of printed cards from the game completely.
I don't consider anything that happens in the current format "skillful", especially when it doesn't even interact with the other player and is limited to deciding how to solitaire your broken engine cards to get the result you need.
They'll probably have to give us more of those same stage 2 glass Cannon cards to even hope to get close to ex Pokémon in terms of damage potential. Maybe the design space is shut down now, but I'm not creative enough to think of a solution to that problem of big, basic pokémon still being as dominant as ever.
At least from what I understand. I have yet to get a lot more experience under my belt to understand the nuance there, or whatever the card game is lacking to control the 2 prizers a little better.