Fine, I’ll be the counter argument:
I wash my wetsuit in the washing machine. NOTE: Front load, not top load: top loads with an agitator absolutely destroy everything that’s put into them. Front load are quite gentle. Top load without agitator, I can’t say.
I do this probably every three months or so. I virtually never pee in my wetsuit, so that isn’t the problem, but I dive in a freshwater river near my home and the suit will definitely get funky. Yes, I could probably use some of the biological enzyme soak stuff, but I’m lazy. I chuck everything in the washing machine with Costco brand detergent. Works really well. Delicate cycle, medium speed spin.
Could it damage my wetsuit? Maybe. But I’ve been doing it for the past several years, and I haven’t noticed pulling my suit out of the washing machine in any worse shape than I put it in. Besides, the diving that I do is completely infested with zebra mussels, so they’re 1000 times worse than what the washing machine might be doing to my suit.
For the record, my suit is a 15+ year-old Tilos 7mm 2-piece. This is old school neoprene: none of that “hyper stretch“ nonsense, this is good, old-fashioned stiff-as-a-board no-stretch neoprene as God intended.

. It’s possible that stretchier, more fragile neoprene may take more damage. I can’t say.
TRIGGER WARNING! I also wash my dry suit in the washing machine. Admittedly, I’m a lot more nervous about this than my wetsuit, but again, so far I don’t seem to have pulled my suit out of the washing machine in worse shape that I put it in. I have a DUI CLX 450. For that one, I turn the suit inside out (neoprene socks FTW) and run it through the machine. Again, I haven’t noticed any deleterious effect on my suit. It just smells better.
I see a lot of people hating on using a washing machine in this thread. My question is: how many of you have ever done it? Or are you just echoing your emotional “gut feeling“? Like I said, I’ve been doing this for something like three years. So far, so good.
Many of you have commented that manufacturers say don’t do it. Honestly, they probably know what they’re doing, and they’re probably aware of specific issues. I’m not actually arguing against that. But like I said, I’m lazy. And so far, it hasn’t bitten me in the butt.