It's the most used card in the entire format; everyone abuses black decks because they include this card.
It's also a card that protects combos or fair interactions against black decks.
It's unacceptable that Thoughseize exists alongside Unholy Annex, Fable, etc.

I only ever face stupid black decks in Pioneer that abuse this card. It should be banned instantly, but I suppose Wizards of the Coast is afraid of losing the few players who play Pioneer since almost everyone runs black.

If there are no bans, fewer and fewer people will play Pioneer. They could also ban Lotus Field for Simic Scapeshift while they're at it.

If there were at least a card like Veil of Summer to force people to play less Thoughseize, it would make sense, but they banned it, like cowards who don't want anything that could balance things and make magic play fair.

Of course, Izzet is also a problem, and Azorius Control desperately needs buffs.

In short, Pioneer is garbage. If they leave it as it is, people will gradually abandon it for cards like Thoughseize, since it's not fair in this format in any way.

Perhaps it's also the hand generator, which always puts 2-3 Thoughseize cards in the opponent's hand, and then they play their garbage without giving you any way to interact with what they put onto the field or draw better than you.

In short, if things continue this way, I hope Pioneer ceases to exist due to the lack of players who desperately want to interact fairly. Thoughseize in this format isn't fair, not in this format.