Browns' TEs taking apart our C.J. & Buck on man-o-man coverage had one personal positive for me. It showed me that even ILBs who lack raw speed can be elite as they usually are. This exposed how much of what they do is everything other but speed - reflexes, smarts, good instinct and good tackling. Because some of these I can develop.
To put it into perspective, Sunday was humiliating, even for them, but I try observe league ILBs because it's the position I play and unfortunately, speed is not my forte.
playing defense is most about anticipating what is going to happen and then try to make the play.
not sure how much you can study your opponent but understanding what the offense is trying to do will speed up your hadeling. in due time experience should help you with that to.
usually if linebacker has good instinct and awareness he/she can overcome his/her speed when trying to cover