>no one will be stupid enough not to use a client like that.
Twitter allows exactly that (or used to, unsure if the API is still up): an API for third parties to use it's content and make alternative front-ends, like Nitter. How many people use them? I don't know, but I'd bet my liver (non-binding offer) it's a minuscule fraction of it's users.
Browsers allow to purge just about every ad from your Internet in a handful of clicks. How many people use them? A mere 27% in the US [0]
Non-Chrome mobile browsers allow extensions to purge ads too (savvy Google killed the Chrome store as they couldn't just kill adblockers, yet managed to stay dominant.. power of brands). How many people use them on Android? A laughable 14% [1]. Of which a fraction will be ad-blocking.
People are not idiots, but it's just not as simple as "offer an ad-free/superior alternative and people will flock to it". People are creatures of habits, if they learned to go to twitter.com or facebook.com, it doesn't matter how much better your alt-front-end is; even if you don't have to compete with the network effect as you'd share the backbone, it will be a steep, steep uphill battle to gain traction.
0: https://www.statista.com/statistics/804008/ad-blocking-reach...
1: https://netmarketshare.com/browser-market-share.aspx