I would say, IMO you don't ride that much so increased volume alone would almost certainly provide you with improvements. As for your average speeds, they look okay. Quite good tbh.
If I was to recommend some turbo sessions that you may benefit from I would say, a 1 hour tempo ride at ~80-85% MHR building over a few weeks to 2 hours would give you a good return on the time spent. You can also do this outside, tbh outside is preferable because long durations of 2+ hours on a turbo get uncomfortable in my experience (I rode at tempo for 2.5 hours on my TT bike on the turbo on Sunday, it was unpleasant to say the least).
Additionally, you could look to do some sweet spot training, this is essentially high tempo/low threshold work (so a little above ~85%) MHR and is called sweet spot training because it is of a high enough intensity to increase your FTP, yet a low enough intensity to recover from reasonably quickly, so you can repeat it more than once a week (but don't do it every day) thus getting the best return for the time invested. You can ride these as two intervals of 20 minutes with a 10 minute rolling recovery in the middle, or as one block, I prefer to just ride for 45 mins at this intensity and call it a day. I don't need or appreciate the downtime in the middle running it as a 2x20.
I would not suggest riding full threshold sessions or VO2 max sessions, and definitely not anaerobic sprint efforts.