We are a commune of inquiring, skeptical, politically centrist, capitalist, anglophile, traditionalist New England Yankee humans, humanoids, and animals with many interests beyond and above politics. Each of us has had a high-school education (or GED), but all had ADD so didn't pay attention very well, especially the dogs. Each one of us does "try my best to be just like I am," and none of us enjoys working for others, including for Maggie, from whom we receive neither a nickel nor a dime. Freedom from nags, cranks, government, do-gooders, control-freaks and idiots is all that we ask for.
I had been hearing how good it is for a while, so I have been giving them a try.
There are two versions of Crossfit - the Fitness version (general full-body fitness - "functional movements at high intensity") and the Sport (the cultish, extreme, heavy weight-lift) version. I do the Fitness version. It is a tough, exhausting group workout where people of all ages (I see age 16 to age 80) and all levels of fitness (fat ladies) do the same thing like a team, but each at his or her own level of ability.
In one of the sessions I like to go to, we have a blind guy. Also, a guy who had a stroke, and a couple of guys who have had heart attacks. It is good fun, bonding, and everybody helps and supports each other. It is also inexpensive, and a good place to meet gals. One of the cool things about the program is that you never know what they will have you doing. It's varied, so it stays interesting and challenging.
It has been surprising to me how quickly your body can respond to these sorts of demands. There are now 10,000 Crossfit "boxes" in the US.
Having tried it as an older but moderately fit guy who wasn't much of an athlete I would give it a qualified thumbs up. I tried it for about a year but quit the box I was attending mostly due to logistical issues getting there on a regular basis. As with many fitness activities the personalities and strengths of the coaches/instructors will make a big difference so if you have options in your area you might want to try more than one place. I think they do get an unfair rap as being 'extreme'. I personally saw little if any evidence of that. As you said, they were quite accommodating to various fitness levels though you are going to be pushed harder than you would be at a place like Planet Fitness.
The box I attended did a lot of free weight work (I think this is somewhat standard in Crossfit). Since I had never done anything like that I struggled to learn techniques, and I've got a bad shoulder that makes overhead lifting difficult. Overhead squats are nearly impossible for me with any kind of weight.
I would have preferred to find a mixed cardio/strength training program like the one I attended for a couple of years in Iowa. It alternated kickboxing routines and resistance bands. To me this seemed a little bit more flexible for various fitness levels, and the resistance bands did a good job of strength train but were more 'user friendly' than free weights.
At the ripe old age of 60, I am the oldest member, by 20 years, in my CF gym. One thing to remember, CF gyms are as different as snowflakes.
Each gym has its own personality and emphasizes different things. The first one I joined was run by a former NFL player. It wasn't for me and did not fit my needs although I did like the overall philosophy. The gym I am currently at is lead by a former Navy vet whose overarching commitment to all participants is "No one left behind." What that means in practice is when I am bringing up the rear during a long run (the normal state of affairs), the folks that have already finished will double back and walk/run/stumble along side of me until I finished.
No one makes fun of me - it's pure encouragement for which I am very grateful.
Likewise, I provide encouragement when some of our smaller athletes are struggling with deadlifts.
Mr. Smith - interesting you've heard we don't discuss injuries. Our gym talks them over routinely with a eye to scaling the exercises to minimize impacting the injured areas.
I've been doing this for about a year. I can see continuing on this path for many years. For me it's a lifesaver.