It is going to be really hard to say if we should have picked Jones or MacKinnon. Both are going to be excellent players for a long time.
IMO the Avs' pick is going to be evaluated on external factors rather than on Jones vs MacKinnon. By this I mean if the Avs defense really continues to suck and never gets better, people are always going to say "Should have drafted Jones." But if EJ establishes himself as a #1 and/or Bigras ends up a top pairing defensemen, people will think that MacKinnon was the correct pick.
All I can really say is that if Bigras can end up as a top pairing defensemen (really big assumption), the Avs made the right call. This is simply because the difference between Bigras and Jones would be less than the difference between MacKinnon than say De La Rose/Dauphin/etc. I think the odds are that either one could have been the right pick at #1, and really Barkov could have been thrown in that group as well.