Your gains will be slower and your plateaus will occur more often. This is one of those things where you just got to spend time in the pain cave to see the returns. You’ll still grow though, it’s worth keeping at it. And maybe in a year your schedule will allow for more time, and you’re building a big base in the mean time.
Have you thought about trying to break the sessions up to help mentally. So, for example, a 1 hour session might include intervals, so a 10 min warm up and 10 min cool down at the end, so there’s only 40 minutes of “work”, but the rest period in between the intervals isn’t really work, so that could be 20 minutes of easy spinning, so in reality in an hour you’ve only got a difficult 20 minutes, so each little block is like a tick in the box and it soon over.