I'm not brave enough to be one of the people who sail or work on a boat I couldn't easily get aboard if they fell over the side, so I regularly check that I can get back aboard our boat unaided and without using a rope or the swimming ladder (which isn't fitted permanently).
Years ago I we did some practical work on MOB recovery, and since then I spoke to the ex US Navy guy who was head of safety for US Sailing. He was one of those involved in the excellent system that reports safety incidents, and presents an annual prize to the boat that has handled them best.
The problems of getting people back on board is one of the reasons I dislike the emphasis on PFDs. Apart from the fact that you can easily die wearing one, they do nothing to help the problem of getting people back on board - and those of us who sail small boats will know how much the bulk and friction of a PFD and its straps etc can increase the difficulty. Lifting someone out of the water vertically (ie with a halyard) can also cause death because of the stress on the body.
I had an incident a while ago when someone rather large and unfit jumped off a boat moored nearby and found himself unable to swim against the tide. There was no way in the world he could get back in my dinghy when I got over to him so I had to motor and drag him to his own stern ladder. Given the conditions (at the mouth of an estuary) if I didn't have the outboard we would have ended up out to sea in a 7' tinny, waiting for rescue.After that little bit of fun, and an experience many years ago when a guest went swimming and was too heavy to get back on board, we now don't invite people who weigh too much to help themselves.
A SUP, SOT or windsurfer does help enormously (as we have found when friends are swimming or we are recovering one of our DOBs- one of the dogs can be relied on to fall overboard once per cruise) and it would be interesting to see if some independents tests showed one of them to be as useful as it has been for us at times. Off the top of my head I'd guess that a small inflatable SUP with a quick-inflate system, or even a decent pump, could be an absolute lifesaver, especially if it was specially designed to also take tethers, straps and lifting tethers. I think the powerboat racing guys use an inflatable stretcher, and the SLSA and tow-in surfing jetskis use a mat. Even if the MOB was just lying on a big boogie board they'd probably be suffering less hypothermia, have their airwaves higher above the water, and it would be easier to pass lifting lines underneath them.
To me the most important thing is the simplest - practise! If you practise, even in middle age you can get yourself from the water to the deck of a 36 footer unaided, or (in my wife's case) by reaching up to grab a line and use it for a sling. Sure, if you're wearing heavy wet gear and tired you may not be able to do a "self rescue" unaided, but you'll make it a lot easier for others. Anyone with practise bodysurfing or cleaning their own hull etc will be able to swim in chop for a long while without getting exhausted, and getting wet weather gear off in the water isn't hard if you've practised it. Even potentially-fatal cold water shock is something you can alleviate (and cure) with practise.
www.outdoorswimmingsociety.com/how-to-acclimatise-to-cold-water/#:~:text='The%20secret%20to%20acclimatising%20to,at%20the%20University%20of%20Portsmouth.