I like TR because it is purely a training tool. I ride time trials and ride a bike to race. Yes I love going out in the sun to ride but I consider myself a performance first cyclist. So yes 2 hour SS sessions are boring in the winter but I do them with plenty of heavy metal because I know they make me a better rider come race season (whenever that will be!). Same applies to o/u and VO2 sessions. For zone 2 I try to get outside with my mates in the winter on a Sunday for 4 hours unless the weather is crap in which case 2 hours SS it is. In the summer I usually race Saturday and do 4 hours zone 2 Sunday. Currently I’m doing 3 - 4 hours zone 2 most days with a VO2 session to keep me fresh. So if 90 mins is your turbo limit then outside it will have to be - you need to see the big picture. If you want to stay fit and enjoy your bike riding then LV and the odd outdoor ride is great - if you want to get faster after the initial gains you simply have to put more time in. Strength training has an enormous thread with some great advice on here - I would suggest reading it along with coach Chad’s recommendations as well. Unfortunately cycling can’t always be about entertainment sometimes it’s going to hurt and be boring…even Zwift can’t address that - good luck 