I'd definitely say it isn't worth it because as I've stated before, stats generally equal your potential for winning. If castform can fill a role, chances are there's something similar that can do the same thing with better stats. Like if you're wanting a special attacker for a sun or hail team, which I imagine castform's being used for mostly, volcarona and glaceon (underrated) are both better in the same role. And on top of that, sun and hail teams are bad so you shouldn't be playing one in the first place if you're intending to win.
If I were to personally make tiers of team (and yes I know tiers are contentious and essentially useless in any given medium), I'd probably give this meta as:
Tier 0:
Anti-Meta Goodstuffs Solid, solid team designs basically look at the kind of thing Ruben runs. These are the kinds of things that win tournaments so yeah.
Anti-Meta Rain My favourite team <3 I think it's the most reliable for a regional and I enjoy running it.
Tier 1:
Pure Rain It's just got everything it needs to succeed at a lower level. Noobs don't know how to beat it; it's got brute force; yeah it's just built to storm regionals. The trick to improving it's to not have too much redundancy in your Pokémon, which can elevate your team to being an Anti-Meta Rain Team.
Goodstuffs Done right, a goodstuffs team is just flat out good. Can't knock it.
Trick Room Now I personally have never liked trick room because it can be countered, especially with team preview, but it's another one of those ones that's pretty good at stomping noobs provided it doesn't get haxed. Slow pokémon are always open to hax so if you choose to use trick room, be aware of this and don't be a whiny bitch if you lose to crits and flinches.
That dick-ass team with the moody and the stored power musharna, hate this one you have to win by beating him before he sets up or getting a crit before he kills all your guys. This team is really terrible and I hate it since the entire thing is luck-based, but I've given it a high tier rating because it's effective.
Tier 2:
Pure Sun It's alright, but never going to make waves in a tournament setting. I mean yeah it's alright but I just have little faith in it. Someone win a tournament with it and I might change my mind but the meta just isn't favourable.
Decent variants of most kinds of team (like maybe Trick Room Rain) basically a team which is good but let's be honest you're just trying to be different, there are more effective options available.
Tier 3:
Pure Hail Unfavourable meta, full of redundancy, frail pokémon: don't bother.
Pure Sandstorm It's pretty rubbish and I don't like it at all. Stuff like tyranitar and garchomp are predictable, and the team sorely lacks OHKO potential.
"omg im so original look at my amazing anti meta team its gravity rain/anti trick room/baton pass/some shit" Please don't do this.
That's how I'd generally places the things going around at the moment. I've ranked stuff on the potential of how good their build can be, by the way. As in, how good the basic strategy is behind each one.