Personally, I think AMD have done a great job in the last few years with their Ryzen CPU's but sort of messed up the motherboard/chipset side of things, and I've had a hard time finding something that fits my needs. Money isn't an issue, but even without that.. I've had a hard time finding something that fits my needs compared to a 6 year old Haswell motherboard that I've never had a problem with.
X370 is actually my preferred choice in terms of peripherals, USB, SATA, PCIE etc. X470 is good too. Not a fan of X570 (get it? haha). I was going to stay with X370 but AMD said recently they wouldn't support them. Maybe there will be unofficial or beta BIOS. So I picked up a an X470 as a backup. Now I'm looking at B550, and I understand the general premise of this thread and pretty much agree with it. But not just for B550, but for all of them.
The compatibility and upgrade options for AM4 are great, but it's also kind of a mess. There's one B550 that appeals to me, the rest are undesired. But it's a bit like that with all of them.. a series of compromises. The reason I care about 4000 series compatibility is because it's the last CPU for AM4 socket.. and years from now, I'll most likely wish I had one. Or to the very least.. I will wish for the potential of that option.. whether it be buying used, at a discounted price.. whatever. It's the strength/advantage of AMD over Intel, but it's become so complicated with so many question marks. And the B550 series doesn't do much to solve it.
By the way, there's more than just a chipset fan issue with X570. There's an idle wattage inefficiency compared to other chipsets, and since I use my CPU 24/7 a lot of the time.. that matters (over the years, the extra wattage adds up). There's also a SATA transfer bottleneck when it comes to random 4k reads and writes. There's been improvements in other things over the last 12 months (PCB, VRM, asthetics), but in a lot of ways, they've gone backwards for my needs. There's more options when it comes to using m.2 drives in raid at high speeds, but outside of that.. some of the other options have regressed. Maybe I should be looking at Threadripper platform and what I/O options are out there but that's a huge jump in price.. when all I really need is 8-16 cores.
So it's a big thumbs up for me on the CPU side, and a big thumbs down on the motherboard/chipset side. I don't even need PCIE4.0, but I need plenty of PCIE and SATA expandability. If you look at the B550 Gigabyte Auros Master, that is the exact polar opposite of what I need. Where as the ASUS Crosshair Hero VI is perfect. Perhaps the answer is to keep the 3000 series CPU and be happy with it, but in a few years the lower latency and extra performance of the 4000 series could be beneficial. While waiting for the DDR5 based systems to improve effeciency and for the price to reduce. On the plus side, I'll have lots of spare parts to build a second "spare parts" Ryzen system, and having two systems is great for troubleshooting if any hardware problems arise. And 5 years from now.. who nows what the motherboards will look like. Who knows if you will even be able to buy a case or a mouse that doesn't have glittering lights all over it.
See I “almost“ bought a Gen4 SSD(MX500) but ended up going Gen3(970 Evo Plus) because despite being just Gen 3 it’s still faster across the board except in reads. So while I can make use of Gen4 it doesn’t actually benefit me in the end. Nor will my 5700XT benefit from a Gen4 slot. Nice to have but offers no ”extras value” or was part of my purchase decision(okay it was until I searched for an M2)
Same, I prefer Samsung Gen3 over the Gen4 options. Samsung will have Gen4 options out soon but they won't be cheap.
AMD have put a whole lot of stock into Gen 4 (with a ton of downsides) that doesn't even have many real world benefits, outside of 4K video editing or other similar things. In a few years, the GPU side might kick in and there might be an advantage but even then, it might only be on the top end GPU's that most can't afford. In the meantime.. it's all a bit "blah" for me.
Something else that's rarely talked about.. is that these m.2 drives run hot vs SATA SSD. The Gen 4 drives run even hotter. Especially if you have a heap of them. Heat inside of a case is a bad thing. Especially for noise. During a game, the GPU fan noise might be blocked by the sound of the game itself but when working on something, there's less noise to cover it up. There's an arguement for SATA SSD, if you don't mind the slower speeds. In terms of Windows loading times, it's not that much slower than M.2 NVME. I went with the same Gen 3 drive as you did (one of them).. but my point is.. I'm not in a rush to add three of them onto a board, having Gen 4 would be even worse. But that seems to be where the motherboards are headed.. where they are assuming that everyone wants to do that.