We've been talking about this in the
Indoor & Stationary group and everyone has their preference one way or another. I've been Zwifting for 3+ years and I would rather be riding outside but the Canadian winters are long, cold and dark so an indoor option is good. I have a wheel on smart trainer with an older (2010) road bike with trainer wheel on it which works fine for me. This poor bike is chained in the basement and doesn't see the light of day (sometimes I feel sorry for it) so it's super easy to throw on shorts, shirt and start Zwifting.
I find it makes a big difference to utilize what they have to offer. If you want to improve something, be it sprinting, hill climbing, endurance, etc... then start up one of their training plans (all part of the subscription). If you like to get the competitive juices flowing then join a race and mash your a$$ off to try and win (but good luck!) or if you just want to move the legs then meander through one of the maps and enjoy the scenery.
The longest I've ridden was 1.5 hours and then I'd had enough. I was a complete ball of sweat and could barely grip my bars any longer without slipping off but what a work out.