They already have a subscription model for this: Twitter Blue https://blog.twitter.com/en_us/topics/company/2021/introduci...
It enhances the experience on Twitter for those that desire more features: a thread feature (which is /really/ nice IMHO), ability to cancel tweets after send, more color themes and customizable icons, etc.
The Twitter "as we know it" will likely always remain free and ad-driven, but if you want an enhanced experience, you're going to have to pay for it. And that's fine by me.