I’m not sure why you want to buy a comic when you don’t enjoy the writing. I’d assume it’s a connection to the characters, and a general desire to keep up with them.
As always, this is your choice. But the idea that there are books that “always sell the same” is nonsense. Every title has its ups and downs, no matter how popular it may seem. UNCANNY X-MEN is hardly an exception, and it hardly bulletproof. if it sells well, that’s because a lot of people are buying it, and presumably enjoying it.
I would never, ever advocate you buying something you don’t like. So this really does come down to your choice.