"Not fun" is an extremely subjective metric to go by. This is competitive Pokemon, you adjust to the game or you flunk out. Rain stall is powerful, sure, but it's hardly the end-all be-all. For one, just try running hail on a random water type. Or you could run your own weather. Or you could incorporate a wall breaker like mixed Hydreigon.
Unless you're suggesting rain stall is overly centralizing, I don't see why it should be removed. I don't find it to be, since there's a plethora of ways to deal with it without compromising your own strategy, unlike, for instance, how Excadrill made Hyper Offensive completely nonviable. It's like any large threat in the metagame; you have to account for it to be successful. Just because you have to account for it doesn't make it ban worthy; it's when you have to account for it in very specific ways which make entire play-styles nonviable that it's banable.
And as people already mentioned, figuring out a simple way to remove it is no easy task. You could just ban drizzle but then you lose all the other rain-dependent play-styles as well, which is undesirable since you're losing more than you're gaining.
I disagree with the bolded statement. Do you understand how many viable play-styles there are in 4th gen?
I would have to say that you'd gain more play-styles than you'd lose by banning Drizzle and Drought. To handle both, you have to run
very specific Pokemon, who almost always suck for anything other than countering Drizzle/Drought. I'm thinking of how rain forces players to use Celebi, who I have used and it quite frankly sucks for anything but handling rain players. As for Drought, you just outright need your own weather starter.
Slapping a Tyranitar on some random team will likely harm the other members of the team.
Even so, I've lately been seeing some sun teams with Ninetales paired up with Dugtrio, so it's not that easy to use Tyranitar to counter weather now is it?
For one, I'd like to see Drizzle and Drought banned. It would allow for the viable creation of teams with this thing you may not have even heard of: Team synergy. I'm getting sick of seeing people able to dominate just by slapping together a team with Politoed, Tornadus, Dragonite, Scizor, Ferrothorn, and some random filler. That's honestly what you call a metagame? I have used one Pokemon that can OHKO both Scizor and Ferrothorn in the rain with a Fire-type move: Specs Typhlosion. Don't get me wrong, Specs Typhlosion is amazing and it's just about as easy to see coming as it is to see the Spanish Inquisition coming. But honestly what player is going to use it just to be able to do quite some damage to rain teams? I imagine Specs Heatran could do the same thing, but Heatran's so slow and even with its superior bulk, it's probably not gonna have many chances to live an Earthquake from a Magikarp if Magikarp could learn Earthquake. (lol)
A wallbreaker sounds like a great idea in theory, but the problem is that your example (mixed Hydreigon) is kinda suckish. Try mixed Salamence. Mixed Infernape's performance is hindered by rain. Mienshao is theoretically a good wallbreaker, but let me remind you that Mienshao has to use this move called Hi Jump Kick, whereas rain stall teams like to use this move called Protect.
Sure, whether or not a metagame is "fun" is subjective. But honestly, you've got all the weather abusers and the Drought + Chlorophyll crap and rain-boosted Hydro Pumps and Thunders, and at the same time you wonder why people talk smack about 5th gen OU?
