To actually be able to do hard workouts at high % of ftp you need to have some form built up (rest day before) and likely after.
Also, if all you do is hard as you can nonstop for 30min for workouts you’re only going to improve that part of your physiology. You won’t have a nice vo2 engine or base.
Research the word “periodicity” and “specificity” as it relates to cycling.
Read up on a site like Fascat or TrainingPeaks or something. Listen to the podcasts.
For now, choose what you want. Pick a plan or coach to guide that work, and do it. Learn the lingo as you go.
Hint: even in running runners who race 5k’s actually don’t do 5k’s all-out every workout. Actually, they do so rarely.