There is so much untapped potential in Twitter. An ad-based business model was the only proven option in the late 2000s, but in the era of Patreon, Twitch, Substack, and Onlyfans, the landscape has resoundingly demonstrated that the old wisdom of "no one wants to pay for content on the internet" is no longer true.
Making something people want to pay for, of course, is the challenge, and Twitter Blue is a very limited start to that. But for the position Twitter has come to occupy in culture, a bold product vision could leverage that to incredible effect.
Twitter has two subscription models. In addition to Twitter Blue (which you mention), they also have "Super Follow", which is more analogous to Twitch/OF subscriptions, in that you pay a bit to a specific creator, so you get a bit of perks from them.
The fact that you don't know about it should say something about how enthusiastically the feature was received. Most creators are probably happier with their existing Patreon/OF platforms.
Do people really like having everything on one platform like that? Personally I kind of like having things separate and companies just do what they do well.
Making something people want to pay for, of course, is the challenge, and Twitter Blue is a very limited start to that. But for the position Twitter has come to occupy in culture, a bold product vision could leverage that to incredible effect.