Average score lowering is one slow, long, hard slog. At least for me it has been. I can shoot a 10 under on 18 holes / 5 under on 9 holes and my average drops a paltry 0.01 point.
I contacted Support about this, and the response I got was not only vague but confusing. Ultimately, I was directed to search this forum. More vagaries and confusion awaited me here and I never got a direct answer.
I inquired because I have been at Legend for over five years and have only been able to lower it to just over 64. I would need to get to 60, or so I believe before I can reach Tour Legend! As far as making Champion or Tour Champion, I have no hopes whatsoever. But then, to be honest I am not trying that hard. And obviously, I'm not that good of a player.
However, I know doggone well that there are many players who have circumvented the process of lowering their averages yet have progressed to the upper tiers. Example: when I view my opponents' stats and see that a Tour Champion has an average score 150.00 and has played only a very few, if any ranked games, it raises a big question in my mind. I even once IMed one during play and the response I got was quite indignant.
So, I formulated a theory, and I don't think it qualifies as being "tin-hat". Players who have low (or no) number of ranked games played and are at Legend or above are WGT paid / compensated employees. I know this for a fact because I once played against another opponent with questionable stats whose username was "IncreaseProfits". I am not BSing. I even IMed him about it, and he replied, "It's what I do." That player's account has long since been deactivated, so don't bother to fact-check me.
I'm hoping that one day I will wake up to find that just like magic, I have advanced to a higher tier, simply because of the number of ranked games I've played. But I sure won't be holding my breath...