For me it's a multitude of issues.
1. At some level, I don't need it. It's the wrong solution to the problem - the right one is being a little more organised.. and asking yourself "How often do I really do this?" I have 8TB of archives of old work projects that I literally never look at... all kept for that "just in case" moment.
2. Storage requirements - this eats up 1/4 of my drive. I have better use for this space.
3. Hardware requirements - have we forgotten that a lot of computers can't even run Win 11? This adds yet another new hardware requirement. Also, not pleased that MSFT also chose this as the reason to try and push ARM on everyone when ironically Intel JUST added NPUs (and AMD is about to). Worse yet, apparently they didn't let Intel in on the secret that to be a Copilot+ PC, you need a 40TOPs NPU - so all of use who bought Ultra Gen 1 CPUs just got screwed.
4. Security. Yes, I know it's not supposed to use the web - but that's thinking one dimensionally. It's building essentially the file equivalent of a browser history. You don't think that's a prime target for hackers and malware?
5. Stop emulating Apple's bad ideas! Or at least emulate their good ones. This is Apple's Time Machine, just done badly.
6. Accuracy. Most analyses I've read on gen AI accuracy suggests it can be as low as 53%. My own experience tends to mirror that. Windows Search is already amazingly bad and resource hungry - this requires an actual extra processor to work.
Seriously, I would rather MSFT had put the effort into getting Win 11 finished and filling in all the missing features and weird UI/UX decisions - many of which they'd already tried before and failed - rather than gluing in yet another massive, disruptive lump of something no one asked for.