Why can't Kirk have a counselor on board of TOS-era Enterprise? because it is the single WORST idea brought on by TNG-era Roddenberry and crew...ESPECIALLY that they gave the counselor a seat on the bridge right next to the Captain's. With all due respect to Marina Sirtis, every single time her character in her official position came on, it immediately applied the brakes to every story...To make sure the counselor had some part to play in the episode, the Captain has to be less of the character he needs to play, that of a decisive leader...
Please STContinues and Phase 2 filmmakers, jettison this concept and any characters associated with out into deep space , like YESTERDAY!!
The reason it was so bad in TNG was exactly the reason you said, because she was a telepath she was on the bridge giving the captain advice something we didnt see any of Betazoids doing!
She always felt out of place and should have been doing Counselor type duties in Sickbay which is exactly how they have written this character.
Theres advising the Captain when hes having a crisis of conscience which is the job of a Councilor, a job we saw McCoy and odd other characters do in TOS - and then there was Troi's job which seemed to be the Captains go to girl when he wanted to know what someone was really thinking, which was most episodes!
This type of character is exactly what some people seem have been wanting from a Star Trek series for a while, a ships chaplan type character just without the religious angle which could and would alienate crew members. Someone people can go to and talk to when they have gone through the things the average red shirt goes through on a day to day basis and something both TNG and DS9 tried but didnt succeed with.