When exactly were those days?
I think
@Gradine made a good point upthread in that individual Jedi can be good, smart heroes. Think Luke, Obi-Wan, Yoda, Kanan Jarus, Ezra, Ahsoka, and so on.
It's the Jedi
Order that's the problem. And yes, maybe some of it was in our heads. When all we had was the OG trilogy, we had to imagine what the Jedi Order was like because it no longer existed.
But then Lucas showed us what the Jedi Order was like in the prequels and the Clone Wars cartoon. Suddenly we were faced with an institution that took babies from their parents to indoctrinate them in a "no attachments" philosophy. An institution that had become hopelessly entangled within the Republic's political morass as its official peacekeepers and eventually army generals.
Armed with this new information, people began evaluating and deconstructing the myths we had built up when all we had was the OG trilogy.
I suspect that when some people say they miss the "good old days", they are referring to the pre-prequel days when people didn't question the assumption that "Jedi = good, Sith = bad".
There's probably also an element of "I miss the days of my youth when everything was more black-and-white. I don't like the shades of grey that come with adulthood."