ph does matter, but you don't have to watch it like a hawk with good products. spot checking all that is needed, unless some part of equation changes.
e.g. your tap water shifts from 8.4 to 7. that's a large enough change that could influence some mixtures...
a well-buffered product will laugh in the face of such a change. my nutes steamroll over that shift and still coem out to the same pH as before.
however, i don't use nutes in my early irrigation of clones or when i sow a seed. I did however still ph-down, because my nutes were not doing it for me, and i killed 0 worth of seed. It is important to spot check. in this context, 8.4, the previous norm for my tap water, was not suitable for sowing seed. i had to ph-down. i neglected to spot check and i ph-downed 7.0 tap water to god knows what.. probably 4-something... few seeds survived.
this guy below that never had a ph problem probably uses products that are buffered or the soil mitigates whatever he ignorees... bottom line his ignorance of the important of pH is not why he has had success. he's lucky enough that his water hasn't shifted or his products are simply ph-buffered.
it affects availability of nutes within the plant. the wrong pH despite plenty of N or P cand cause a deficiency. this is consistent and repeatable causality. anyone who doesn't beleive in it is either willfully obstinate or learning disabled.