This was just one of the many mis-steps of RTD that led to the end of the classic series.
Actually, that had nothing to do with it, as shown by the ratings trends for the final few years (upwards in fact). JNT was responsible for the classic series lasting as long as it did. The BBC always intended to kill of the show as it could no longer compete due to budgeting in a ST:TNG world. The final few seasons were scheduled in literally the single worst time slot available (opposite the heaviest hitter on the schedules) and given no promotion. It was not uncommon for
fans to only find out the new season was on halfway through.
The myth that JNT killed Doctor Who really needs to die off. It ran longer than most entire series under his tutelage (as long as the X-Files for example, which is a pretty long-running show). The two most often selected examples - the casting of Colin and the overall McCoy era - are not borne out by the facts. Season 22 was actually
popular with the general audience and the ratings trended up (to say nothing of critical response) during the final two McCoy seasons.
Scheduling, lack of promotion and the 1985 hiatus (from which the show never really recovered in terms of ratings) killed off Doctor Who. All three of these were down to BBC brass, which could only budget for an entire season what Paramount was budgeting for a single episode of ST:TNG.
Remember too UK audiences loved the TVM and it rated far better in comparison there than in the US. What made it work more than anything else after the relaunch was money. The BBC was prepared to budget, schedule and promote it properly. You could run the new series in the same death slot, with a corresponding budget and no promotion and it'd die just the same.
Fans should be thankful JNT staved off the inevitable for nine bloody years
and managed to pull off a creative and critical renaissance. Not many can say that.