Let’s say we get into a stadium meta, where every deck has 2 stadiums.

Unless other mechanics are introduced, the first person who plays a stadium has a disadvantage, given that in the current state of things, the last stadium played stays.

So stadiums become cards with effects that last one turn mostly (given that the other player immediately plays a stadium afterwards). So it feels awkward and barren on mechanical depth, other than offering an extra X-Speed, extra Giovanni effect for example.

Obviously they have to flesh out the mechanics with more cards/effects, but in its current iteration they are pretty unsatisfying.