For me, Search for Planet X still feels too big a box for the game. It’s not so much a standard game in a slightly smaller box, as a small box game in a slightly smaller than standard box. It’s a deluxified version of a back of a magazine puzzle! Almost the entire game is just a pad of paper, everything else is just frivolity. They’re similar to roll and writes in that way.
As with a lot of games the size of the board was the limiting factor. Otherwise could have easily been the size of Welcome to or the small/medium Osprey game boxes (King is Dead 2nd ed, or Cryptid). I don’t think many people would consider Ganz Schon Clever with a large board as reasonable. Considering the amount of information the board provides in Planet X, it does not need to be the size that it is.
Moving away from my spicy hot hot takes…
More generally, I kinda dislike the direction these conversations lead. I like that boxes give space to expansions. I dislike games with perfect size boxes and decent inserts that don’t fit the expansions in, with expansions inevitably having boxes that are too large for their contents but leave no choice because they don’t go in the core box (7 Wonders Duel!!!).
I love love love Pandemic, because the first expansion includes an insert that fits the first AND second expansions in the core box perfectly. Rarely see that level of forward planning. And it makes me not want to buy the third expansion, because where would it go?!
Having games with slimmer boxes would be appreciated for storage, but I don’t think general ‘size’ makes much of a difference. There are only two types of sizes: those that need to go on a shelf, and those that can be thrown in a drawer or box. As long as a box fits on the shelf, width and height are kinda irrelevant.