I would suggest just getting a Roku and using it for awhile before making any big decisions about leaving anything.
You need internet (from someone.) Since you say you are a long-time committed customer of Xfinity, I assume that means you have other choices for internet. That is to say, I assume committed doesn't mean compelled!
Many apps are independent of any cable system, but certain name-brand channels that you are used to on cable may only be available if you also have cable. This is why I suggest you just get a Roku and see what's what. You may care about losing those channels or you may not. I think a person could just get Netflix or Prime and have more TV than he could ever watch. But it might not be the exact TV that you wanted.
Of course, there are also "cable replacement" type packages like YouTube TV. Though I think YouTubeTV is priced relatively close to what Xfinity gets for cable TV. It's hard to compare since channels and features are never exactly the same. It really comes down to which channels and features you care about.
Of course, Over-The-Air hasn't gone away, and you can get TV from satellites, etc...
