Like most things, the answer isn't black and white. Having had
lots of experience on these kinds of sites, here's my experience. I'm in my early 50's and like younger women...don't we all!

In short, they can and do work. It requires patience, a good profile and it helps if you're at least reasonably intelligent and in good physical shape...and you most certainly need a sense of humour!
AFF- very hard work but definitely some genuine women and I've met several, but that was quite a few years ago....but many fakes.
POF - Met several women and ended up in a 1 year relationship with a gorgeous woman 20 years younger.
Shagbook - Don't know what it is like in recent years, but when I was using the site about 10 years ago, I got REALLY lucky and met a beautiful (and very naughty!) 29 yr old woman. We lived together for several years.
TheAdultHub - going back 15 years, had several successful encounters. Most exciting one was a woman who came to my house and shared a bath with me five minutes after walking through the front door.
Fabswingers - Most recently used ( and hopefully the last!) and I found lots of real people and probably the most reliable in the UK. I struck way too lucky again and met a gorgeous woman aged 30...actually fell in love!! Before meeting her, I met several women and a couple and had bucket loads of fun
BeNaughty - used many years ago and got a date to chaperone a woman to a sex club in Birmingham. I believe the site has changed significantly since then and people I knew seem to have migrated to FabSwingers.
In summary, even if you're an old git like me (ok, I am pretty good for my age and physically fit) there are younger women in their 30's who are willing to meet significantly older guys....as long as you're in good shape and can interest / intrigue them...and ultimately convince them you have something good to offer them.
None of the sites make it particularly easy for you but from my experience, pretty much all of the major ones do have some genuine women to be found. Don't forget also that there are couples that like to meet single guys...and believe me, that can be A LOT of fun and a hell of an adventure. I've done that on 5 or 6 occasions and met some absolutely stunning women and often, their husbands just want to watch.
My advice...Don't give up and don't accept the 'It's all a scam' posts. Understand it requires a lot of effort, but be in no doubt, there are some absolutely stunning (and very naughty and fun) women to be found if you look hard enough. However, be realistic....if you're overweight, don't look after yourself and can't be bothered to invest the time in getting to know a woman before trying to get her in your bed, it's not going to work! You get out what you put in. As of today, I suggest you check out FabSwingers as it seems to have plenty of genuine women and it's not too expensive. In fact, quite a bit of functionality is free.
This is a genuine post and I don't usually respond to topics in forums, but I thought I should give hope to those that believe it's ALLa scam. It's not.