Ford probably demanded that Han get killed off, so if a reunion didn't happen in TFA, it wasn't going to happen at all
While many of the decisions in TFA were questionable from a trilogy starting standpoint, they did aid in making it as huge as it was
However, without those choices, I'm not sure Johnson could have done as well with TLJ
Because Abrams is so dedicated to the mystery box and refused to answer questions or even, y'know, basic plot setup decisions, Johnson had pretty free reign to interpret things as they stood
So he was able to give Hamill an amazing role, present Snoke however he liked, and set up a frankly amazing third act
Either option Lucasfilm had for the third film (keeping Trevorrow or letting Johnson have an extra year so he could do Knives Out) would have been better than bringing back Abrams