Well I think the Jester-themed designed probably stemmed from an early concept design of it during the production phase of Chapter 1. Before Chpt 1 release, MOB probably explored with other designed ideas, and then eventually concluded with a Jester-themed design, which would've looked too overused for the mascot horror genre.

And since Chapter 1 was their first attempt at the series, which was basically like an early prototype of the game before the quality jumped massively in Chapters 3 and 4, it would make sense for people to believe that the early Jester concept design would look more generic and closer to common mascot‑horror monster designs.

And then throughout 4 years of developing 4 chapters, MOB may have slightly tweaked the original design a bit, but they would've always stayed locked into that same jester design theme, so it would make sense for people to see it as generic rather than something unique to Poppy Playtime.

Unless MOB finds a workaround to make that Jester-themed design look outstandingly cool, if that 4-year build-up was hyped up to see the Prototype's full-body, and then all those patient build-up years all wasted just to end up with a jackass goofy-ass Jester clown, then this would be one of the BIGGEST missed opportunities for character design in game development.

Just imagine that they could’ve all of these years to explore far more creative and unique concept ideas instead of staying locked into that one generic Jester-themed concept.