It runs like a Pentium 4, really boggles my mind that Apple would go this far to make Tahoe useless.
👋🏻 SDAVE,
Out of curiosity, have you tried partitioning off a bit of SSD disk space and making a clean install of Tahoe?
It's a few hoops to jump through, sure, but might be worth it from a 'peace of mind' perspective, even if it's just "yep, just as laggy". Perhaps a Sunday project?
I don't think Apple deliberately trashes their older Macs, but all optimizations will be for newer hardware, of course.
I had to shed a tear after finally getting the dual W6800 Duos, just as Blender was getting GPUs to work on macOS..... and even Apple was directly involved to make Blender + Metal work as intended.... only to read a few months later that Blender is dropping the Intel + GPU support for the Mac.
In the case of Blender, I know for a fact that it had nothing to do with malice or "we don't care". I worked directly with a few devs and went through many personalised builds to find out exactly where the problems/bottlenecks were. In the end, we reached the point where Blender is now: 4.2 LTS is the last version my Mac Pro will run.
Ultimately, it becomes unsustainable to patch software for individual configurations.
In Apple's case, I imagine it's pretty similar on a daily basis, on a much larger scale. I'm sure the software leads make continuous, unceremonious decisions about where to draw lines and cut features/support, trying to see the big picture. And the more niche the product/feature is, the more these types of decisions tend to hurt.
Owning both a Mac Pro and a MacBook Pro M3 Max, I try to stay balanced. I would lie if I didn't admit I'd like to see my Mac Pro and its GPU power extend further into the future. There is a LOT of grunt to tap into on the compute side of things, but software keeps moving away from it. The CPU is what it is. I'm not even sure it's worth bothering with the 28-core upgrade, which has become cheaper again.