Your experience diverges from that of other experienced devs who have used the same tools, on probably similar projects, and reached different conclusions.
That includes me, for what it's worth. I'm a graybeard whose current work is primarily cloud data pipelines that end in fullstack web. Like most devs who have fully embraced LLMs, I don't think they are a magical panacea. But I've found many cases where they're unquestionably an accelerant -- more than enough to justify the cost.
I don't mean to say your conclusions are wrong. There seems to be a bimodal distribution amongst devs. I suspect there's something about _how_ these tools are used by each dev, and in the specific circumstances/codebases/social contexts, that leads to quite different outcomes. I would love to read a better investigation of this.