Yes, but you have to take it in context. If you are wanting to build a top-of-the-line gaming PC around the RTX 3080 or 3090, you won't want to cut power supply short. With a stock clocked Core i9-9900K, I'm seeing power draw at the outlet of up to 525W running games -- situations where the CPU isn't fully loaded, in other words. Overclocked and running something that loads up the CPU and GPU would probably get my test PC up to 650W. Because of rails and just for margin of safety, I'd never want to run a PSU at 100% load. Having at least 20% more power available than necessary is a good practice.
Now, swap out the Core i9-9900K for a Core i9-10900K and overclock that. Unlike the 9900K, which might see peak power draw in the 150-175W range, 10900K could easily hit 250W or more when overclocked. Momentary spikes can go maybe 100W higher than that, and the same goes for the GPU. Toss in the rest of the PC and heavily loaded CPU and GPU could get you into the 750W range -- again, overclocked -- with spikes that might near 1000W. 20% extra would mean 1200W.
You also have to factor in that PSUs tend to degrade in quality over time. A brand-new high-quality 1200W PSU can certainly put out 1000W and even 1200W. Three years down the line, you'll probably lose at least 10% of maximum power. Plus, if you're spending $750 on a GPU, $500+ on a CPU, $250+ on a good motherboard, and $250 or more on case, storage, RAM, and cooling ... well, at that point I wouldn't skimp on a PSU and pick up a $100 model just because it's probably good enough.
So, 750W Gold PSU running on a Ryzen 9 3900X or Core i9-9900K? Yeah, you should be fine. You might come close to the limit, depending on other components, but at stock I doubt you'll have issues. Overclock the CPU or GPU and I'd definitely go with at least 850W, and at that point it's not too much of a stretch to get 1000W or 1200W.