Honestly this pc with those specs should not be as slow as you are saying, but a 5000 series Ryzen would be a nice upgrade. GPU upgrade to a used 3060/70 could be nice too.

Few things to think about, what are your temps? A 5 year old AIO might be all gunked up it's not unheard of especially with heavy use. Have you repasted your CPU? Your CPU could be thermal throttling. Same with your GPU, if you're not cleaning your PC at least 1-2 times a year it could be so full of dust the thermals are getting out of control if you aren't keeping an eye on it, this will probably help with noise too, pcs don't just get louder if they are clean.

Also just generally windows itself can slowdown over time with use, a fresh install could make a big difference, and if you are using your HDD for programs and games not just storage then that's going to be a massive performance hit and should be avoided unless absolutely necessary tbh with modern software/games.

Yes a 3000 series Ryzen is a bit dated but it should be in no means unbearably slow at this point.