I’ve come across that take before. With respect to the Janissaries, I’m not really sure they were part of any sort of balance of power; it would be more accurate to say they were a state within a state - not a good thing. They killed Selim III for trying to modernize the military, for instance. And the First Serbian Revolt was kicked off by renegade Janissary troops slaughtering Serb aristocrats in an effort to stop the Sultan from allying with them to take power.
With respect to the Tanzimat, now that’s a better take. The Tanzimat was overly centralizing, and in a multi-ethnic non-contiguous empire, that’s not the best model. And the “tolerance” of the Ottoman Empire was only ever a relative thing - sure, by the standards of the seventeenth century it was, but not in any modern sense. As mentioned, the First Serbian Revolt, a pre-Tanzimat affair, was kicked off by a slaughter of Serb aristocrats. Beyond that, during the Greek War of Independence, which was also pre-Tanzimat, the Ottoman government killed the Orthodox Patriarch of Constantinople in a highly humiliating manner as a “retaliatory” measure for the rebellion of certain Greeks he had no influence over; this move proved massively alienating. This is not “tolerance”. There is a case to be made that without the Tanzimat the Ottoman Empire might have collapsed “better”, but there would still be plenty of horrific massacres.