I don't think anything is inherently wrong with blockchain technology, but what it's been molded into (a purely speculative profit driven ecosystem ) is a waste of it's potential.

In theory/research papers, it's not a terrible idea, a few years ago, 3blue1brown on YouTube did a video about how blockchains and cryptocurrencies work at their core, setting the controversy aside. It is a currency that is actually tied to something of immutable valuable, time and logarithmic growth, and would require much more computational power than any singular entity could control over 50% of. Those goals are good goals.

The the irl problems come in on multiple aspects however, there are only so many graphics cards made every year, so people purchasing for mining impacted the entire market of graphics cards spiking prices higher and higher, they run on electricity which is still generated with a lot of fossils fuels, and cards that break because they're running all the time and are staying hot end often up in landfills, where lots of useful metals are just sitting and rusting away.

The notion that any "Web" technology (i.e. user-facing publication, sharing, & discussion) needs to be coupled with a fraught¹ payment system seems like a fundamentally contentious issue, mostly introduced by people who stand to profit from the success of those payment systems regardless of benefit to Web users.

¹ Regulatory issues, cut-and-run scams, and so on. Some blockchain services have turned out to be securities regulation violations. Some have turned out to be outright frauds where the issuers have just run away with "invested" money. In any event, nobody should today be relying on any blockchain service when creating forums or other services intended for the general public.

The problem with Blockchains is most of the projects associated with them are scams until proven otherwise. It's kind of like Western Union transfers, money orders, or iTunes gift cards, nothing wrong with the technology behind them, but when the topic comes up, I immediately think of scams.