Not every team right now runs entry hazards, and not every team runs Rapid Spin. Entry hazards would be pointless if and only if every single team out there had a Rapid Spin user. But since not every team has Rapid Spin, entry hazards aren't pointless at all.
I don't know how else to explain it. It's this presumption that not every team uses one, so not every team uses the other that keeps both mechanics in each case viable and necessary.
Among the variety of ways that weather could be balanced, I still believe one of the ways to balance the power difference between weather teams and non-weather teams is to implement more ways to get rid of weather. At least between different weathers, all it takes is a simple switch-out or move use to cancel out one weather and summon another, so there should at least be a move use or a switch out of the same variety used to cancel out all weather.I dunno, maybe we'd be better off if weather was completely gone, but I feel like if it were more balanced and less over-centralized it would be fine.
Since the weather moves are status-based and don't require a Pokémon to be dealt damage, so too should the move that cancels weather entirely. Of course (and I can't stress this enough), it would be distributed at a rate similar to how Rapid Spin is distributed now to avoid literally every single Pokémon having the potential to cancel out weather. Otherwise, pretty much every player would say, "Hey, I have a spare slot for this Pokémon!" or something to that effect, have an excuse to put "Rapid Spin 2.0" onto one of their Pokémon, and make weather pointless.
Field effects, such as Gravity, Tailwind, and Trick Room, however, are a different story. As far as the discussion of over-centralization goes, I think weather takes higher priority than these.