But what's the value in it? I'm trading Bitcoin and related ecosystem (from ETH or DEFI nowadays to crypto related securities like MARA, RIOT, CAN, etc. I always hold some crypto) since 2012 and made very good returns compared to the initial investment. But never ever saw a widely adopted use case for any coin other than speculation.

There are always promises, wishful-thinking, hypothetical demand for a use case but it never materializes. Here are some:

BTC: Trade (edit: for goods and services)? No use since price is too volatile. Store of value? Tell me again after this bull run. Besides, what's different than LTC, or even Doge that defines a different value proposition?

DEFI: The infrastructure is there but people just use it to speculate. Never heard a real business borrowing in DEFI to finance, for example, shop renovation. The only use case I can come up with is miners borrowing to buy miner hardware, since returns will be in crypto and will be implicitly hedged against crypto price inflation. Other than that, trading SUSHI or UNI or whatsnext is the only way.

NFT: What happened to CryptoKitties between last bull run and this one? NFT actually guarantees the uniqueness of the outer shell, not what's inside. Rare gaming items might be a use case, but why a game maker would use something it can't control, or fully extract value is beyond me.