This would be broken if not for a little thing called commander tax
Overall, Amethyst, Ruby, and Steel are more focused on attacking while Amber, Emerald, and Sapphire are more supportive, but each can be used to make interesting combinations and people can experiment with seeing what strategies work with their personal play style
That's a big old player base too as Pokemon revealed this week that we've collectively collected 40 billion cards between us
As far as this iteration goes
This ability stops the opponent from evolving their active Pokemon, meaning all setup will need to be done from the bench
Last but not least, I still haven't managed to pull off the infamous Squirrel Nest / Earthcraft combo and it's definitely on my Commander bucket list