My TE is eventually reaching the cap I wanted to keep him at to train secondary skills and I was wondering what a TE needs besides agility, catching, and blocking. Are positioning and vision critical in his development? If not, I would then just max out his catching. Thank you for your time.

my TEs improved with positioning. but i also train vision.

you could also train carrying and footwork and play him as a fullback as a secondry playing position.