My experience is limited but here is my 2 cents worth:

I started with Shimano SPD dual sided pedals and MTB shoes with single-release cleats. It took me a couple hours of intentionally clipping in and out frequently while riding around quiet residential streets to get the hang of them and I had a couple of failed clip outs over the next few weeks. BUT I have come to blame a lot of the (minimal) problems I had on a lack of knowledge on my part rather than on the clipless system.

I have since gone to multi-release cleats and learned to set my pedals' retention springs to the lightest release setting that prevents accidental clip outs. I position the cleats to ensure intuitive clip-ins so I never have to look down to position my feet. I found the sweet spot in the retention setting so that I never have an unintentional clip out but can easily step off the pedal, without intentionally clipping out, in any direction except straight forward or back. I can even clip out pulling straight up but with a bit more force than I generate on the upside of a pedal stroke. There is absolutely no way, short of a freak mechanical failure, that I would remain clipped to the bike in an accident. When I come to a stop all I feel is a slight click as I put my foot down sideways and when I start again, my first downstroke results in a slight click back in without any fiddling around.

IMHO, most people who have tried and hate SPD clipless probably never adjusted or at least properly adjusted the retention springs, leaving the middle of the road factory settings, and/or used single release cleats that used to come with just about every SPD shoe. If I had known then what I know now, I probably would have adjusted to clipless in much less time and avoided a couple of Arte Johnson style tip overs.

You can certainly ride without any form of pedal retention, and I do so often, but I can say that properly adjusted SPD provides some advantages with virtually no downside.

When you first get SPD pedals, read the instructions and understand how to adjust them, same with the SPD multi-release cleats (which thankfully are being included with many shoes these days). Like any newly installed equipment, take a bit of time practicing and dialing in the adjustments with the bike sitting still and supporting yourself with a hand on a fence or post. Work with cleat position and retention adjustments until you can clip in and out smoothly and intuitively, this shouldn't take a lot of time. If you need someone from the LBS to help you they will usually be happy to do so. It really is a short learning curve until you will clip out easily without any conscious thought at each and every stop or even if you get into a situation where you have to dab a foot down quickly.

I can't speak to any other retention systems as I have only used SPD with dual sided pedals and MTB shoes.

Nightshade obviously doesn't like ANY clip system, which is his choice and he has every right to his opinion. But I disagree that clipless retention systems are ONLY for racers or wannabe racers. I find advantages to them for everything from no-drop group rides, charity centuries, fitness/training rides, commuting, MTBing/Gravel Grinding, or just plain pleasure riding. I'm happy to ride the flats of my dual sided pedals in athletic or light hiking shoes, but certainly don't find that any safer or more comfortable than clipping in.