Yes buddy, I’ve been there several times over the years, and it’s perfectly natural. Would be bizarre to not suffer diminishing returns - though I think for endurance athletes what likely happens is we lose that top end pleasure from the activity and maybe even forget what it feels like. We perhaps roll around on a maintenance level, where they need the activity to simply feel okay.
For me, my burn out happened because I wasn’t really enjoying where I was riding. It was pretty miserable where I lived to be honest. I was just riding to keep weight down and training for power that I didn’t even need for anything.
Solved that by moving though! Wish I’d done that years ago.
I was off the bike there for around 11 months and just started again recently - in the best place I have ever experienced for cycling and love every ride. Not much traffic, cars are friendly and seem to enjoy watching you ride and struggle up gradients! I have a variety of climbs and super long flat scenic coastal areas etc all at the doorstep and the roads are smooth.
I built a beautiful super bike too, and I love looking at it and riding it.
It’s really kickstarted my joy in cycling again. Only made possible right now due to WFH flexibility - I actually sneaked away and rented a place in the countryside to pull this off!
This for me is what the future should be like. Able to move around travel, while working and riding in beautiful locations when you want.
Bit of a tangent - but long story short, I went from feeling miserable about riding to absolutely loving it again.
Oh also, I’d also throw this in. Fitness didn’t seem to leave me as catastrophically as I thought it should. I know the theories and studies on how fast different attributes tail off and how long it should take to regain that fitness - it didn’t seem to be like that for me. It came back much, much faster than expected.