My experience may be slightly at odds with others, but I'm enjoying Zwift on a dumb, wheel-on trainer.
Before lockdown, I couldn't be bothered with trainers at all. I'd had some rollers back in the day, and hardly used them. I began to think again because it was more difficult to get out; because, after a little incident involving a double bypass last year, I was under strict instructions to take regular exercise (and I suddenly found myself neither cycle commuting nor able to go to the gym that I had joined); and because my cycling club started to promote Zwift club rides and so on, in the absence of normal activities. I think it was also a factor that, in the gym, I'd found that I preferred the virtual-reality ride routes on their static bikes and walkers, rather than watching TV like everyone else.
I still wasn't going to spend a fortune, so I dug out an old fixed-wheel bike and got a dumb, wheel-on trainer from my son-in-law, who had a spare. I rather liked Rouvy, which uses real-world videos, but signed up with Zwift because that's where the club was. I've got hooked. I'm now doing more of Zwift than the long walks I was doing at first. I'm also on Zwift more often than out on a real ride, because an hour or less on Zwift seems worthwhile, whereas I'd rather go out for at least half a day on a proper ride, and my need for utility riding has dropped to almost nil. To be fair though, as people pointed out to me early on, there are loads of videos on YouTube and the like, of social and training rides and routes. If you're not bothered about your effort level relating too much to the speed at which you travel, you can just put those on a screen and "ride" along - that's what they are for - without any need for a subscription.
You do need sensors on Zwift, at least if you have no power meter - speed, cadence and heart-rate. I don't have a pain cave - just a mild-discomfort patio outside - so a PC screen isn't practicable and I use a fairly basic Android tablet mounted on my stem. That set-up was pretty good for me. There's no variable resistance, but I look at it like this: you spend a lot of money so that Zwift can make it harder when you're going uphill. Then, you use variable gears to make it easier again. Or, you stick with a single gear, and imagine that Zwift made it harder, then imagine that you just made it easier again. You still end up going really slowly uphill, and really fast down, either way, and pedalling at about the same rate throughout as you would with all that extra kit. Maybe I'm missing something, but I've still not been convinced of what
The thing that did get frustrating was the speed I was going at. That's probably specific to my individual trainer and readings - it's hard to tell. But I did seem to be a lot slower than in real life, and longer rides and bigger hills were taking impracticably long. After posting about this here and in one or two other places, I got a very generous offer from another YACFer on an older power meter, and I'm now using that - but still on single-speed (it's a freehub type, so I'm using a single-speed convertor). The effect of that on my speed has been remarkable - I've actually overtaken some people, and I'm now probably faster than in the real world - but otherwise, my previous paragraph stands.
I haven't done any of Zwift's training programmes, just the various rides that it offers. But you do get hooked on collecting the badges for completing different routes. If you do Audax, you'll understand. And you can get hooked too on collecting enough "drops" to "buy" faster bikes and wheels. Or, if you prefer, to "buy" classic steel ones. And there's a feature that my club, at least, call "the elastic", that keeps you together on group rides, so that you sort of go at the average of the speeds of all the individuals - they dragged me up the Col du Zwift to the radio tower my first time, rather like, decades ago, schoolfriends dragged me up the Cat & Fiddle my first time there.
As has already been said, there's a wide range of rides to join, or you can ride alone (as I usually do). You're encouraged to interact with others - the equivalent of shouting "Dig in!" or similar is to give a "Ride on" as you pass, or are passed by, others. And the club are now trying to get me involved in riding some virtual club 10s - our usual inter-club series with some other local clubs has also moved onto Zwift.
Anyway, that's me. YMMV, as they say.
