Is it worth leveling servants with a S grouth to max level?

Well, that is up to you if you have enough ressources to spare on this servant or if you need to level up another one. If you have few materials or EXP card, it is better to use it on another servant.

if you're in a position where you need to budget resources then maybe not if you don't like the servant very much, but otherwise I wouldn't really put to much weight on it.