>>58849924People want to judge games with the hindsight that we have now, but at the time, we didn't know that the series kept changing itself and straying further and further from the original games. So gen 5, when it came out, was the first game based on a non-Japanese region, and we had no reason to believe this was going to be the norm from now on. It brought a lot of changes to the series, the designs feel very different, the plot feels different than previous games, there's a bigger focus on characters, etc.
At the time, there was no reason to believe those things were going to be permanent to the series from then on.
Imagine an alternate timeline where gen 6 is actually a return to form and every Pokemon games on Switch is similar to the old school games, just with better graphics. What would be the perception of gen 5 then? It would be the cool unique game that did things differently. It's not the exact Pokemon formula, but that would be its appeal.
Of course, since the rest of the series just doubled down on those changes, a lot of people now see it as the harbinger of those changes.
To contrast with another series, look at Zelda (pre-BOTW). There was a formula established with ALTTP and OOT that most of the games afterward followed. Except Majora's Mask. Majora's Mask is the weird game that did things differently. And it gets to exist as this cool weird game because the rest of the series didn't double down on what made Majora's Mask different, they just went back to the OOT formula after.
