One modern board game design convention is that simultaneous play is an outright improvement over taking turns. The argument typically goes that it speeds games up without diluting interaction, reduces downtime, makes you lunch, slices, dices, etc. And there are plenty of games that seem to support that point of view - hell, one of my favorite recent titles is Pocket Paragons and that game is basically nothing but simultaneous card flips.
That said I disagree that it's as simple as "do this instead of turns". Not too surprising, I'm broadly against hard and fast rules like that, but this is one I feel pretty strongly on. Interaction is notably less pointed when you process everything all at once. It often feels less like an intentional attack and more like an accident when someone impacts several other players at once. There are folks for whom that's a benefit, but I'm not one. Perhaps more notably, there's still plenty of waiting for your turn as the game's pace always matches the slowest player. With all the complaints of analysis paralysis in board games, is that really a benefit when everyone's subjected to it all the time?
Like any other design consideration simultaneous play isn't simply "better" than other methods. It's another tool in a designer's kit, a different kind of play than turns, one that comes with pros and cons. The only right answer is the one that makes the game the best it can be.
