Not seeing improvement in certain exercises

Hi Blenders,

I'd love to hear your advice. There are a couple of exercises that I do not see the progress in for three years, i.e. I still can only lift as heavy weights as I did three years ago. While I've been seeing progresses in most other exercises, however slow they are, my reverse fly and lateral raise have been in plateau for like forever.

For both, I can do only a few repetitions with a clean form with 8 lbs per hand, and then I need to shift to 5 lbs per hand. It's not the amount of weights itself that concerns me the most but it's the fact that I have been in this exact state ever since I started taking weight lifting seriously. I just don't see any hint of getting over the hump. I get so jealous whenever I see trainers like Tasha or Nicole using like 12 lbs per hand for reverse fly😐 cuz I usually can lift more or less same weights with them for other UB exercises.

Will I eventually see progress if I just keep working out? Or is it possible that my lateral deltoids already hit the max strength?

Has any of you experienced the same with any exercise? I'd appreciate any tips you can share, whether they are about these specific exercises or your experience in getting over the plateau in general!

Edited