It seems, no, DEC did not miss the PC boat due to one person's nearsighted view.
Microvax was 1985 and yes it would have been interesting if they had a low-end personal product based on VAX at that time. They did have the Professional [0] around 1982 based on PDP-11 which I used at school to learn Macro-11 assembly, C and Pascal. It was blazing fast and ran RSX/11 which was years ahead of DOS. They also had the Rainbow [1] around 1982 (maybe marketed to officework) with a z80 and 8088. And then there was the VAXMate in 86 which we don't talk about :). So it seems these were all aiming at the new "PC" market in a scattergun manner but nobody really knew what that was at the time.
0. https://en.wikipedia.org/wiki/DEC_Professional_(computer)