Tbf, the people playing on difficulty 10 are usually rocking meta builds like orbital napalms, thermites, and explosive crossbows. I doubt there's many people playing the hardest difficulty with the Constitution and Sterilizer and unironically calling it balanced. And then when people see certain weapons under-performing on harder difficulties, they assume it's a weapon balance issue (especially hating on light pen weapons), but I don't think it is. At least not in most cases, there's definitely a couple stinkers. I think it's more of an issue with the game's RNG.

Because if you get unlucky, you just won't be able to use half of your loadout. For example, when diving against the terminids, you can get unlucky and get a hive guard seed or a bile spewer seed, where those are 75% of the enemies you encounter. Which is a problem if you happened to bring a light pen weapon or two, which are basically unable to hurt any of their heavily armored bodies, especially not in mass numbers. Or you could have brought a bolt action rifle against the predator strain and suddenly you're stuck in a death loop.

The game desperately needs a way to either outright select the seed you want, or at least make specific seeds more common on certain planets or biomes. Because as it is, you're more or less just encouraged to only use weapons that are generally good against all enemy sub factions, lest you get fucked over by RNG.