Really? Who on their mind would put a 5950x or a 3d in a b350 motherboard? Why the heck would you do that? We are talking about people that keep their cpus for a long time, right? So these people will be stuck with pcie 3 for the next like 5 years? Losing on faster drives / performance increases in new gpus and possibly direct storage.
Also, who on their right mind that keeps their cpu for 5 to 7 years buys an almost 2 year old cpu? Cause thats how old the 5950x.
X370 and b350 are completely outdated right now and besides the 3d every other cpu that is supported is 2 years old. So yeah, not a great option
Who? Everyone in a tight budget that already feel they are going beyond their budget for a 5900X/5950X/5800X3D or whatever they are upgrading to. You probably never had financial difficulties forcing you to do very specific upgrades. Everyone who would just want to upgrade their CPU without having to mess with also a motherboard upgrade. People who don't think like you are perfectly fine and their mind is also working perfectly fine. Not having difficulties sleeping at night because you have a PCIe 4.0 motherboard instead of a PCIe 5.0 motherboard, is understandable. Being them, felt that, ....when I was 20-25 years old. Got a bit late in the PC platform, at about 1998. I was losing my sleep for buying the 333A Celeron instead of the 300A that could hit 450MHz with a simple bus change.
Stuck with PCIe 3.0 means 3GB/sec speed. Not exactly the end of the world. On graphics cards PCIe 3.0 X16 is perfectly fine. You are right if we are talking about 6500XT. Are we?
Upgrading to a new CPU, when on a tight budget, doesn't mean going to buy the brand new model that came out yesterday. It means going from a 2600X for example to a 5800X now that 5800X's price is much lower compared to when that CPU came out. Or even an older 3900X if multithreading performance at the lowest possible price is needed. A 5950X is also at a much better price point, but probably who even needs a 5950X will go for a newer board.
But then again someone who can't just upgrade the whole platform does have the option to upgrade only the CPU. For example someone without technical knowledge that uses that 2600X mentioned before, needing to upgrade to something much much better calls a technician at home to get some offers. And hears
"Replacing the CPU will cost the cost of the CPU plus an extra 30 euros for the work. Replacing also the motherboard, will increase that cost with the extra cost of the motherboard, while the cost of the work will also go up to 100 euros instead of just 30, because replacing a motherboard and doing some basic testing to see that Windows booted correctly and downloaded all the necessary drivers does mean extra work and the possibility of something going wrong which translates to even more work and more costs for covering the necessary work".
So, there are plenty of examples of people in their right minds avoiding a motherboard replacement just for upgrading the CPU and not missing out on SSDs that offer pointless speeds at much higher prices for the same storage capacity.
Of course there is 6500XT out there that could be an argument in your favor.