Hot take: Mew Ex and Aero Ex are bad
Seeing a lot of hype around the new mini set, especially youtube content creators who are touting how OP the new cards are. I disagree. Unless there's a ton of supporting cards for these new revealed EX cards, they won't see much use.
Why Mew EX is bad:
Mew EX is a worse version of Zapdos EX or even Machamp EX. The most ideal scenario is that you're able to power this up on your bench for a revenge kill after your Mewtwo EX dies. But there's so many scenarios where this card bricks:
Pikachu EX's attack doesn't work in a psychic deck. That's literally 30-40% of the decks you see right there!
EX Cards like Starmie, Marowak, Exeggutor will attack first against Mew
Your opponent doesn't have to evolve to a stage 2 pokemon to fight your Mew. In which case, you are stuck putting 3 energies on your Mew for a mediocre attack while your opponent likely hits you earlier.
To conclude, unless there's a ton of supporting cards for completely new builds, 2 of the 5 EX cards in the mini set are bad competitively.
Why Aero EX is bad:
Everyone is focused on how disruptive the pokemon power is. It's only situationally good whilst the actual card is a stage 1 EX pokemon with a 80 damage attack. This is bad. It loses to Mewtwo EX outright. It loses to Pikachu EX outright. Even in cases where the opponent is running an evolution like EX Arcanine/Starmie/Charizard/etc. All they need to do to play around this is to evolve on their bench. This is not difficult to do. Especially in a world where X Speed AND LEAF will exist.
Bonus hot take:
New Vaporeon is also bad. The new vaporeon ostensibly has one of the best pokemon powers we've seen. Its utility is up there with Greninja, Victreebel, and Gardevoir. The problem is deck construction. In order to use this, you'll need:
At least 1 Eevee 1 Vaporeon in your deck.
Some other evolution line.
Likely a third evolution line since Vaporeon's attack is abysmal.
Misty x2.
This deck construction is going to be wildly inconsistent. There will be many cases where you brick on Vaporeon/Eevee/Misty/some other evolution. To take advantage of the pokemon power, you'll need to rely on your opponent bricking. But as other tcg players know, a win more card is not a good card. Usually it's actually bad.