How did they weaken Spock's character? I guess for Sarek and McCoy you could say they showed them old and Sarek's case dying, but I think that had more to do with the fact that TNG took place when these characters were old. I don't see how showing them that way "weakened" them as characters.
I wanted to use the female capacity to avoid an answer to any question but it does seem unavoidable.
In the old canon: "The Making of Star Trek" pp 225-226
"Complete adherence to logic is the primary motivating factor in the Vulcan mental process. Of necessity, complete suppression of emotions is required, lest logic be influenced in any way.
Over a period of many centuries, the Vulcans have both practiced both total concentration and complete suppression of emotions. From the time of his birth, a Vulcan child is taught that to show emotion is highly improper, that it is considered an extreme breach of good taste....Vulcans long ago concluded that emotion was dangerous, set about to repress it and replace it with logic. Century after century, through practice and custom they repressed emotion until they became almost incapable of it...."
TNG portrayed Sarek as suffering from the syndrome which makes him lose emotional control. IMO the old canon says Vulcans HAVE less emotions & feelings than Humans -- not just a matter of suppression, it was an evolutionary process. TNG "Sarek" claimed Vulcans have powerful emotions that they learn to suppress. .
actually that vulcans still have to repress their emotions is present in amok time and other places.
that vulcans suppress their emotions most of the time is why the pon farr exists.