That's a major theme in Pokémon circles. Increasingly, it's accepted that, despite there being around 350 legal fully-evolved Pokémon in the official ruleset most of the time (even more this year), there are always going to be around 12 that thoroughly dominate the statistics. The Top 8 in last year's World Championships featured, out of 48 individual creatures, a grand total of 8 species (one of which only appeared once, in the 8th place team).
And scenes like that have helped the community come to terms with the fact that you can't be quirky and win, let alone use your favourites; although top-level players have always accepted that, I noticed a clear change in attitudes over the last couple of years among the general player base. It's definitely possible to go anti-meta (very few players wanted to risk that in Worlds, else we could have seen a dominant presence from that) but consistent victories are what are required to keep ahead in such a chance-based game, and there's only ever, at best, a moderate picking of Pokémon that can grant those. It's no longer typical to look down on meta-heavy teams; if anything, the converse is true.
Splatoon is a very different game, however. If it were similar to Pokémon in the amount of power imbalance between weapons, I don't know if I'd enjoy it as much, particularly because it's much harder to group shooter weapons into unofficial tiers than Pokémon. But Splatoon is a finely-balanced game, compared to the standards we expect from Nintendo (Smash, MK), and even if some weapons are, individually, simply incapable of winning given firefights in equally-skilled situations or creating as many opportunities for themselves, the level of freedom within a battle in Splatoon means that it's very possible to create winning situations for almost any match-up, and that otherwise lesser-used weapons can fill crucial niches in meta-centric teams. Splatoon doesn't have bad weapons. If anything, some weapons require more support, map control and/or set-up but correspondingly pay dividends.