Prior to TR I followed a coach’s plan which would be similar timewise to a LV plan on the turbo and supplemented it with one hard and one leisurely weekend outside rides and got good success. Initially when I joined TR circa Aug 2020 I was doing a MV plan but dropping the weekend sessions when covid allowed group riding. When I got into the AT system circa Jan 2021 TR support advised me to go on to a LV plan to get TR to calculate correctly and supplement the weekend as before rather than replacing. TBH I could do with doing a new FTP test, ramp tests don’t work for me I’d have to do a 20mins test or similar, but I’ve been happy with the value I’ve got perceived effort wise (with slight tweaks through the season), the pbs I was getting through the season and decided to avoid the extra TSS that might hamper it, FTP is only one metric anyway, results are a more important metric to me. In summary, a similar timewise plan to a LV one with supplemented outdoors rides worked for me and similarly the LV plan again supplemented with outdoors rides works for me too, so I don’t see it as useless 
That’s an interesting comment/observation. I never thought of it that way. My solo outdoor rides, I typically just go pretty hard the entire time trying to keep around a 19.5-20mph avg. speed. I know it’s stupid, but that’s just what motivates me I guess. There isn’t a ton of vertical…maybe 1500-1800ft on an avg 30 mile ride, but I can keep that pace without much issue typically. My experience has been a little strange. Meaning when I first got on a road bike two years ago, I’d only done some indoor spin classes prior, but found I was naturally a really strong rider compared to just about any non-serious rider I would ride with. I guess I am just trying to figure out how to marginally improve within my own time constraints. I want to improve, but never plan on racing or anything like that.
I have a lot of Wed night worlds from my first two years of riding (2016-2017) where the ride was 90-120 minutes and IF between 0.85 and 0.95. Coincidentally that was after a couple years spin classes. What really changed my fitness was consistently putting down 6-8 hours/week. Doing more endurance work the last two years, it is definitely more sustainable (in late fifties) and raised my aerobic fitness to another level. 2021 was about 7 hours/week average. I’ve got data on what’s worked well for me, but everyone is different.
Don’t be afraid to try different approaches, and find what works best for you.
Ignore the ramp test protocol. It doesn’t work for everybody (me included).
They bother because for some, it’s all the time they can commit to training.
However supplementing LV plans with a load of endurance work are probably the best plans TR have to offer the majority of its users. If I only had 6 hours/week to train, I’d pick this over a mid volume plan any day of the week!!
I like the way you’ve articulated something that I’ve found out about myself over the years of summer riding/winter training.
My first FTP test of the winter would start high, then drop, then recover again. Likewise, when I headed back outdoors in the summer, I would initially be slower (despite rise in FTP), but soon improve again.
In my mind I’ve always likened my fitness to a cake. In the summer, I’m building lots of icing on the cake (top end fitness), which helps in that first indoor ramp test. Throughout the winter, the icing gets smaller, but the cake underneath gets bigger. When I head back outdoors again, I’ve not got much icing, even though the cake is bigger.
You worded it much better than my own rambling thoughts though!