Why can't I run fast in practices and time trials?

Dude this is fantastic problem to have.

Far better than crushing workouts and not running up to potential in races.

Don't worry about how you run time trials and workouts if you're performing well in races.

You're not jamin. Give thanks to your Deity of choice.

OP -

This is indeed a good problem to have. I am 33 years old and am the same as you. When I was your age I was the opposite. I could run 6 x 400m and average 67 sec (70 sec standing recovery) but my best times were 2:09, 4:58, and 11:25.

Back to today - I run tempo runs at 6:45 pace and it feels quick. Cruise intervals of 1 mile at 6:15 also feel quick. Luckily I do a lot of strides and short fartlek. I ran 13:40 for 2.5 miles the other day (5:28 pace).

I trained for other teammates then and train solo now.

Back to you - you cannot simultaneously race well and have a pretty training log. The most talented runners can do it, but not everyone

You may find this hard to believe but PR-ing in races is where it should be done, not in a workout or minor time trial. You don't wanna be "that guy" who crushes workouts and can run circles around everyone at practice but completely bonks at races when it matters most. Also, we all have off days.

I had the same problem. I would be killing myself to hit 75's in 400's with 1:30-2 minute rest, but then I ran a pr of 4:48. This was all last year in 8th grade. I eventually got to the level wher my workouts got pretty good, but my races were always a different level, which is where you want it to be, or same at least. Its ok to have the problem you have, but give it a couple years or even just a year and you'll adapt to being a type of runner where you can excel at both.