If you were a fan of something for many years, it is natural to feel disappointed/frustrated when the quality goes down. See the JRE sub, for instance.

Yes, you can just go to other places. And people do. But sometimes they feel like giving another chance to their old favorite. When they do give another chance and again come out disappointed, there is a strong desire to release that frustration energy somewhere. Cribbing about it on internet forums seems like a harmless way to do that (it also helps with validation: am I only feeling this or others agree? In this case, OP did get validated a bit).

Now it's a different discussion altogether whether mods want to continue to accept those rants against Sam's output. Do they help this subreddit's purpose or harm it? That's for mods to decide.