In most cases, sure... but I don't think that it's possible to completely rule them out. For some individual stages, alternate sets can really shine - my usual example of that is the Tri Nouveau, which is pretty clearly inferior to the standard Disrubbler set in most cases, but works wonders on Rainmaker stages with long corridors (Triggerfish, Arowana and Mackerel are the usual targets; the third is especially good, also synergising well with the Echolocator). So I use the standard Tri perhaps 15~20 times more frequently than the Nouveau, but eagerly take up the latter when the rotation's really good.
You're not wrong. There are many weapons that are generally the weakest of their class but on certain map/modes become a more desirable choice. The Tempered Dynamo is generally the weakest Dynamo, but it is probably the best for Port Mackeral (Although Dynamos are still generally bad on Port imo haha). But with the Carbon Roller Deco and .52 deco, there really is no reason to use them over the mains. Seekers are terrible subs and Seeker Rush is the weakest special in the game. Sure it sort of locks down an area for a bit but Inkzooka is way more effective in all the same scenarios. Burst Bombs to deal with ranged foes, ink walls and Burst Cancel kill with are so, SO much better than Seekers. Then with the .52 Deco, you again are stuck with Seekers. Splash Walls open up so many strategic opportunities and can be downright oppressive against certain weapons. Inkstrike isn't totally useless, being decent in Turf War and Splat Zones, but Killer Wail is very effective in all modes and can completely shut an avenue down, or keep the enemy pinned when respawning, etc. Splash Walls/Killer Wail might not offer DIRECT inking advantage the way Inkstrike does, but with their applications towards area control and the plays you can make with them you can generate more opportunities to ink, or for your teammates to ink, to hold objective, etc. It's just a kit that works better in every scenario, because of the options it gives you.
Then you have stuff like the Inkbrush Nouveau, which are straight-up bad. The Inkbrush is a pretty flimsy main weapon, Ink Mines are the worst sub in the game and Bubbler is useless when literally every weapon in the game can bounce you out of your attack range with ease. The standard Inkbrush offers nearly unparalleled turf coverage, but it concedes a lot of ground too because it can't fight and struggles to deal with pressure (Or apply any of it). So the Permanent Inkbrush, with its ability to handle ranged opponents with bombs, as well as use them for positioning and pressure and Kraken to make/stop pushes, performs better in pretty much every situation you'd use another Inkbrush. And I say this as someone who used the default Inkbrush from the time I started playing the game to about halfway through my stint in A+.
I say all this, but I certainly wouldn't want to discourage someone from using a "bad" weapon if they enjoy it. That's their prerogative. This turned into a strangely loquacious rant haha. I guess my point is that there are bad kits in this game, and I don't enjoy playing weapons that impose limitations on me like that. I like weapons that give me options. Not necessarily just top-tier weapons, though. I love the Splash-o-Matic for example but I honestly can't think of a situation where it's actually the best choice out of my stable for a map hahaha. Bluefin Depot SZ, maaaaaybe.