You're right of course. Decentralized or not, a platform needs to solve a problem, without that it's just a toy.
Here is what I'm thinking about - reactions/comments on the Web, discussions about the long-form content. Current options are on-site (too easy to fake/censor), or external centralized (Twitter, Disqus etc). Both aren't perfect - on-site is fake, and external are all closed. I've been waiting for 5 days for a new Twitter API key, and they haven't approved my request yet.
With nostr we could have an open platform for comments/reactions. Upvote/downvote content by posting to nostr, post comments on nostr, kinda like on Twitter, but it's open. Now suddenly a search engine can take into account both signals, just like it uses web links now. Any website can show global unbiased comments on their site. Any app can now use that data to build some great experiences.
Add LN tips/payments into the mix, and this looks much more like a real web3.0.
Exciting :)