My Lenovo T490 is at least 5 years old. It came with Windows 8, a i7-8665U at 1.90GHz, 16GB ram and a 500GB SATA drive. Fortunately the motherboard was fairly upgradable so I upgraded to 32GB of RAM and a 480GB solid state drive. I've upgraded to the latest stable version of Windows 11, 24H2.
I've been pretty happy with Win 11 although one of the more recent major updates caused issues and I had to do a repair install to straighten it out. It did have me worried for a bit. But it worked out fine although it was a bit time consuming.
If I'd been stuck at 16gb of ram I'm not sure I'd be able to run 11 or if it'd run well if it could run it at all. The solid state hard drive helped a bunch too I'm sure but I did that not long after I bought the computer when I saw a deal on the drive. I looked into upgrading the CPU but even if it's possible there is only one a notch faster CPU the board would support and I found it to be surprisingly expensive for what would be an obsolete processor, so no, and I didn't investigate further.
If you don't have a solid state drive and your board will support it, it's worth upgrading. You can usually find a good deal on solid state drives if you look. Same goes for the RAM. Don't ask at Best Buy or even the computer manufacturers tech if the upgrades are possible. They usually just tell you they aren't upgradable. The manufacturers techs tend to be surprisingly ignorant. You have to go to the independent tech forums to find out.
Yeah, Win Xp worked well for it's day. Actually I thought 98 was good too. Some of the others were turds though. Win 8 was pretty good. I like 11.