That isn’t true.
PS3 comes to mind immediately - I’m sure I could dig up others
So the two models of the PS3 that followed the fat PS3 were worse? Or are you talking about how later versions of the fat PS3 got rid of the PS2 back-compat, the extra USB ports, the card reader, etc? I was mainly thinking about the PS3 Slim and the top-loader PS3. I honestly have no idea how good either of them are compared to the different versions of the fat PS3. I just know later systems were more reliable, didn't have issues with things like the YLoD that a lot of launch versions had to deal with. My friend's launch-model PS3 died on him, but I used the BD drive from that to replace the broken one in my refurbed PS3 (which was the first model that did not have back-compat).
PS4 Slim fixed some issues with the HDMI port f*cking up HDMI cables and a few other things compared to base PS4, but I guess I don't really know if the hardware was weaker or less reliable in any way. I was under the assumption it was generally better (lower power usage and heat output, for example).
The first wave of PS2 Slims were definitely worse, they didn't have cooling fans and there were reports of units catching on fire. I have one of the PS2 Slims that has a cooling fan, but the memory card port on that thing is real wonky (doesn't always feel like reading memory cards), and the drive stopped reading discs. I don't have the original large PS2, but good gawd there were like a million internal revisions of that thing. So many different motherboards and internal changes. I was looking to buy one but I haven't figured out which revision is the best one to get.
PS1 some of the early versions had power supply issues, overheating issues, and I forget what else. My first PS1 (which was a later unit but it still had the parallel I/O port) had a drive motor failure and stopped reading memory cards. I replaced it with one of the units after that, which did not have the parallel I/O port. I think the first version of the PS1 also had regular non-system-specific Composite ports (or at least the red/white audio ports). Not sure if you count getting rid of those ports a downgrade. The last version of the original-looking PS1 and then the smaller PSOne that followed after were better in most ways I think.
XB1 S was decently better than original XB1 (and they got rid of the rid ESRAM or whatever it was), and it could even do 1440p which
Doom 64 supported (and maybe some other games). I used less power, gave off less heat, and I think had
slightly faster load times (if I recall correctly, base PS4 and XB1 had SATA-2 but all later versions had SATA-3).
X360 kept getting better with newer revisions, like adding the HDMI port, adding internal flash storage, lower heat output and power usage, making sure newer units didn't RRoD or have E74 errors and whatever else, etc. They did get rid of the memory card ports though, and the physical eject button, with the Xbox 360 Model S (or whatever it was called). I think there was also a final X360 model that looked more like the base XB1. Not sure what's up with that thing.
Original Xbox I'm not as familiar with whatever different revisions there were.
DS got better screens with the DS Lite, newer faster CPU (and possibly other hardware upgrades) and SD card slot with DSi. Original DS had a better larger DPad and was just more comfortable to hold and use. The 3DS was upgraded to 3DS XL (easier to hold and larger screen size) and then the New 3DS (faster CPU and eye-tracking for the 3D).
Every new version of the Game Boy was better than the one before, except GBC has a smaller screen than GB Pocket, and GBA Micro was a definite downgrade in usability compared to original GBA and the GBA SP (and it didn't have back-compat with GB and GBC games). The GBA SP was a nice upgrade over original GBA screen-wise, which it was actually lit (first front-lit then later back-lit). Although I found it more annoying to hold and use than original GBA, which also had better buttons.
Genesis Model 2 and 3 had stereo audio out, but you could use the 3.5mm jack for the same purpose on the Genesis Model 1. Genesis 3 of course had no support for Sega CD, and I don't think 32X works on it either.
One thing I do remember is that later revisions of SNES and Genesis stepped up on the copy protection/region lock, and stopped allowing devices like Game Genie to work on them.
I don't recall all the later revisions of the Sega Master System and the SG-1000, but surely most of those newer revisions were better than the older ones (like the Sega Mark III).
The 2nd main revision of the original Switch got better battery life, but I heard the screen was worse. The earlier Switches have a Tegra hardware flaw that forms the basis of how you soft-mod the system, so I'm glad I got one of those. The Switch OLED is definitely an improvement over the original Switch though, if you use the system has a handheld. Not sure how the screen in the Switch Lite compares to the original Switch, other than being smaller.
I heard later versions of the Nintendo Wii ditched the GCN back-compat, and thus didn't have those controller ports either.
Anyways I'm just rattling sh1t off the top of my head, I don't actually remember specifics. But there are clearly cases where systems got better and got worse (sometimes both) with newer revisions.
