The big thing one has to realize is that for ”real” riding, the general goal is to get as much travel as possible for a given amount of effort. For spin class the purpose is to pack the most amount of effort into a given time.
Variety in training is generally a good thing, so I rather enjoy an occasional spin session.
Even if some of the exercises seem silly.
The one I’m most sceptical about is when you’re supposed to alternate between sitting and standing at the same resistance and cadence.
Doesn’t work for me.
If I pedal seated at a good standing resistance, I blow my knees out in minutes. If I pedal standing at a good seated resistance the cadence will increase unless I counterweight the upward bound leg.