The view of SMB2 has changed over time because many of the people who didn't grow up playing it are controlling the narrative that it's not a "real Mario game". Back in the day, no one cared about that at all (if you even knew about Doki Doki Panic), it was crazy popular and only was eclipsed by SMB3. These new fans on Twitch and YouTube create this new narrative about retro games that were not how it was back in the day. For example, everyone says "SNES (Sness)" now, but back then, I never heard anyone say it like that, it was "S-N-E-S" and "N-E-S" (not Ness). Speed runners also don't like SMB2 because the physics are different that 1, Lost Levels/2J, and 3, and that plays a part in perception.