Really. I can do endurance rides on a local bike/walk path, but actual workouts are hard. I did 4x12 at sweet spot a few weeks ago and it was decent, but nowhere near the structure as indoors. The bike path itself is nice, but has road crossings every 1-2 miles, so every interval had short drops in power as I got close to the intersection (usually blind), and a spike as I started back up. Again, not terrible as I could get ~80-90% adherence to the interval, but not indoor training level. Plus there were a few times I had to slow to pass walkers taking up the entire path, but I could have gone at a different time to help with that. And the kicker is that it’s 30 minutes one way to drive there, making it hard to justify an hour in the car for an hour on the bike. Which is why I usually only go there for long 2-3 hour endurance rides.
I’d love to be able to train outdoors, just don’t have the area that suits it unfortunately.