Study tactics one theme at a time or all at once?

Tactics trainer here at chess.com give you random problems, all themes at once. I think that may not be optimal. I think it would be better to drill a single theme until mastery, then add another theme, and repeat until you have mastered them all. At the end of the day I think we are just trying to get patterns into our brains. I think if you try to do dozens of themes at once, it will take forever to master any of them. Is there any consensus on the best way to do tactics problems to get the most benefit?

I like that approach. There is a book by Susan Polgar called chess tactics for champions that does this.

I got to 1960 USCF doing one theme at a time of tactics.

One theme at a time. Jack of all themes is master of none.

Is there a better tactics website that lets you do one theme at a time?