I didn’t read Flash’s post as identifying every AFD voter as a neo-nazi. That being said, there are a sizable amount of folks in both AFD leadership and their supporters that lean pretty hard into neo-nazi terminology and positions.
This is just a small sampling of quotes from people high up in the AFD power structure: https://www.dw.com/en/afd-leaders-and-their-most-offensive-remarks/g-37651099
I have a friend (a former chief of staff for a CDU representative) who switched from working for the CDU to the AFD and then back again. His reasons for originally switching were some of the legitimate concerns you articulated. He came back, because in his words, “the AFD is completely insane.”
I think it’s pretty telling that Germany’s domestic intelligence agency has labeled the AFD as a right-wing extremist organization. This party and its rise to power is something that should spark legitimate concern.
Grievance-based politics is a poor platform, whether it's from the left or the right.