Ignore the ram for the moment... Check the drive S.M.A.R.T. status.
Look for corrected and uncorrected errors, if there is ANYTHING in the raw data collumn, the drive is failing and there is your problem. Replace the failing drive before you do anything else.
Then check ram.
As for upgrades,
If this does the job, there's really not a ton of sense in getting something newer. Gaming will see almost no improvement with that gpu and in terms of apps and OS that too will see little, EXCEPT for one place, the drive. M.2 is a pretty good upgrade, but, you do not need a new motherboard to get it, you can buy an $8 adapter that plugs into a pcie slot and gets you m.2 NVME ssd.
Ryzen,
While I want to say wait for the 3000 over the 2000 series, there's a few issues here. For one, it's untested, and two, it's really not THAT much gaster, and three the boards cost A LOT more. The average 3k board is going to run $200, but, you can run Ryzen 3k in most 2k boards with a bios flash. That is an option, but again, there's no tests yet. I do look forward to building a low power model into a teeny tiny box though. So much power for so little wattage. If I didn't have my 8700k, this would be what I'd be buying.
Regarding pcie 4.0, IGNORE IT.
Not even a 2080ti can max out a pcie 3.0 slot, in fact two of them together barely can. The onlything capable of using it so far is the new Corsair ssd and there is very, very few situations where even a high end cpu like the top of the line 3k is going to ever exceed what a PCIE 3.0 ssd could deliver. It's just not the bottleneck.
Which is an important thing to consider...
Where is your bottleneck these days. Yes, you have fewer cores, but beyond 4 you start getting diminishing returns, this is why the 9900k is not hyperthreaded. Firefox can use 4 cores, Chrome really only uses two (and one is just the base browser, the second does the rendering), the OS, yes it can use more, but most of the OS sits idle. I have 12 threads and most of the time my cpu load sits at 1-2% with only 2-4 threads hitting 5-6% and even when I do something half will sit idle. Point being, more cores will not really make a difference. Same with frequency, cpu speeds themselves have not imrpoved dramatically.
Honestly, the biggest improvements since since your cpu, have been more cores (which I already ruled out), ssd interface, which you can fix, and ports. We now have USB type c/thunderbolt. Thunderbolt stuff is expensive and of limited use, type C is just a connector and you can use an adapter, you won't get the fast charge but again, that's not a huge deal and if you really want that, a pcie card can do it. The thonly other real gains have been in chipset and that can't be solved easily, but it's also not THAT big of a deal.
My advice
Check the drives, check the memory, fix the problem.
Want a bit more speed, install a pcie to NVME adapter and install that ($60)
Still not happy, wait a few months for Ryzen 3k to settle in and see if a 2k series board will work, OR look around for someone selling a used last gen setup.