Yes it is certainy possible there's simply a lack of data points but I don't think confirmation bias is at play here; at least for me personally I only know a couple of very senior devs and they all have the same problem so it's not like I'm actively cherrypicking only cases which seem to prove my point (which btw is just 'I see a pattern' not 'everyone who used BASIC once and had no easy access to proper source sucks')

2 data points is not a pattern. An equally plausible explanation is that you’re an environment full of idiots, junior and senior alike, yourself included. Your numerical and analytical skills are not unsupportive of this conclusion.