OP has buyer's remorse. I know how they feel. Over the last few years I've found the more I spend on a PC component, the more likely I'm unhappy with it.
Lately my most satisfying purchases have been very cheap. I don't mean garbage, I mean exceptional value for money.
As an example, look at the case in my sig. It's a quality budget no-frills case I got at a great price, so I feel like it's the best case I've ever owned.
As for the 4090, if someone gave me one free, I'd sell it. Not because I need money, but because I'd never install a firestarter surfboard into my system.
I am going to push back on that.
Firstly, your right, that 100% can happen. And I have had it happen. A certain Samsung curved monitor comes to mind.
But with my last several expensive purchases it has not happened. I have done a lot of research, and purchased poorly anyway. No regrets.
My most direct comparison would be buying my rx6900xt off of AMDs website two weeks after launch. No regrets, none at all. One of my best buys. At the time everyone said buy the rx6800xt, but I have never regretted spending the extra $300 for the 6900. I don't care its only 3% more performance. It has glowy lights.
A very ill timed purchase was a Samsung nvme SSD I purchased. The price dropped right after I bought it. alot. But I am still very happy with the SSD. Knowing it is Samsung, its reliable, its 2 TB, that I will be using it for years, that it has its own heat sink, its pcie 4, that all fills me with the warm and fuzzy. Yea, it had the write age error, but that was flashed so quick by Samsung it was a non-issue for me.
Then there is the CPU. I should have bought a x3d. But I bought something inferior. And that is ok. What is 6% anyway? At some point it is just chasing silly numbers. I still really like the 5900x. So what if I spent more money for less performance?
My point is, I am very poor at making purchasing decisions. But I have grown to really love the parts I have anyway.