I used SLI and Crossfire many times in the past. Shame to see it go away. DX12 multi-GPU is BS. Everyone knew from the moment they announced it that hardly any game developers would bother with it. Now you have $700-1000 cards (3080) that don't even come with an SLI/NVlink connector anymore - so even if you are lucky enough to play a game that actually has working DX12 multi-GPU, it won't be an option for you. With the 3090 being the only card of this series to even have the connector, that is even less motivation for game developers to implement multi-GPU going forward. Sort of like some strange anti-consumer reverse chicken-or-the-egg scenario.
If SLI still worked, I'd probably be picking up a 2nd 2080 right now, used, cheap, instead of worrying about trying to get a 3080.
SLI got me through the cryptocyurrency GPU price-inflation. I had been running 2x GTX680 on an overclocked 2500K. I upgraded to an overclocked 5820K on an X99 motherboard. Since that CPU and board could support 3 GPUs, I got a third GTX680 and ran triple-SLI for another 2 years instead of buying a new card. It worked great for me. All the games I played had/have great SLI support. Combined GPU performance was better than a 980ti. Only catch was being limited to 2GB VRam but I was running a 1080P monitor at the time. I still use those 3 cards in my backup computer, and they still run great with DX11 SLI.
This could be an interesting opportunity for AMD to embrace multi-GPU. Real traditional Multi-GPU, not this "shift all work to the game developers and cross your fingers that they do your job for you" BS. So even if a top-end AMD GPU can't compete with a top-end Nvidia GPU, maybe 2 or 3 together can... Before I ran GTX680 cards in SLI I ran 2x 4870x2 in Quad-Crossfire. That ran just as well as triple SLI did.