It absolutely is imho. Like at some point it was not social media as it became later, following (well, attempting to) the financial success of Facebook and Twitter/X, and instead people could submit long-form answers to questions, rather than merely vomit their feelings into the never-ending stream of others doing the same.
^This
I also choose this guy's wife
And my bow
etc.
By deprioritizing people finding answers and instead encouraging them to make new posts all on their own to ask the question yet again, over & over, spez tried to make money and enshittified Reddit by taking it away from its original purpose that had given it such a reputation for being great.
So it's not "having ads" that destroyed it, but the chasing after ad revenue at all costs that was driving it into the dirt. Even before the protests revealed that starkly to us all that the Reddit we had known and use to love was dead - spez had stolen it, he took our efforts and that ad-bloated, authoritatian-modded corpse was what was leftover. And it wasn't even bc of profits alone, but greed in chasing short-term profits above all else, including long-term profits. Aka capitalism killed it.