Gods, even high level gods, should be capable of affecting their domains. Otherwise what is the point of them? I’m not talking about in-setting, I’m talking about from a game perspective.
If Yu-shan and all its inhabitants are nothing more than distant bureaucrats who can do nothing more than move around paper and be corrupt, then they’re entirely useless. There should be tangible benefits to earning or bribing the loyalty of a god, and tangible risks to annoying one. The god of a river should be capable of making the river flood. The god of a mountain should be able to cause landslides. Yes, both of these cases could potentially destroy your village/town/kingdom if they are within the area of effect.
Hint: don’t piss off gods. Or at least, make certain you have a MAD situation with them. Gods want to flood out your village, destroying all your people’s homes, ruining your crops and dooming them to starvation? Okay. Ghost Eating Technique.
Yes, this makes powerful gods powerful adversaries. Not in personal combat (a pair of Dragonblooded could probably defeat most terrestrial gods of equal Essence handily and they will be no direct threat to combat-specced Celestials) but in a strategic and logistical sense. This is why Zeniths and Twilights and Eclipses exist. So you can bargain, subdue or enslave local gods – and doing so should be a definite and major advantage, worth the time of taking on a powerful deity. You should tread carefully around them, because while you can kill them they can fuck up your shit in a lot of other ways.
There is no need to cast Reverse Gravity on your town to destroy it. A plague god could do it, as could the god who decides your fields will be fallow this year, or the god who decides all carts on the highway leading into your town will suffer broken axles. You might want to make certain nobody is poisoning their ears against you, perhaps with some diplomacy-fu or outright threats. The Immaculates usually manage this with a handful of itinerant monks; surely as powerful Solars you can do better.
And yeah, if you manage to piss off Sol Invictus enough your town may go up in a giant fireball. Sucks to be you.
Extremely large-scale effects beyond the local city level are going to require lots of gods working in unison. So a single deity in Yu Shan probably can’t decide to turn gravity off, but the Bureau of Nature probably could if you decided it would be a good idea to make yourself number one on their personal shit list.
Fucking with powerful Gods should be exactly like fucking with Second and Third Circle demons. You don’t wander around in Malfeas offending Ligier all over the place unless you want your holdings in the demon city to go up in nuclear hate-fire. The kind of Gods who can do stuff like that are mainly stuck in Yu-shan, don’t care enough to bother and would require a massive amount of effort to entice.
But frankly, considering none of this is any more powerful than Rain of Doom I don’t see why letting some Sidereals bribe the right people in the Bureau of Nature to fuck up your shit is that bad. It’s no worse than a Solar Sorcerer showing up and doing it. And there is counter play, that’s why you have Zeniths and Twilight and Eclipse caste Solars. Because not every threat to your city is one that your Dawn or Night can stab to death immediately. Sometimes your Zenith is going to have to pull rank and get his own divine minions to handle it, or sorcerers are going to have to counter it with spells or wards, and Eclipses will forge treaties that no god wants to break because they fear old Sol’s wrath more than Chejop Kejak’s.