I did not suggest that ranking should predict.
My other favourite sport is snooker, very popular here in the UK. Rankings cover 2 years rather than 1. This prevents such massive lowering of a players position unless they are out for an exceptionally long period. It also means they are under less pressure to compete when under strain or with a chronic injury. Also there is provision to protect a player with the agreement of the World Snooker Assoc. This was recently done for Carter who had cancer treatment and it worked well for him and was supported by other players. Wimbledon uses its own ranking system too - I am sure this ridiculous draw would not have happened there. For me the issue is not just about Federer. We are seeing far too many players injured. One of the reasons for this is they are playing so many tournaments to protect their points, often playing when unwell or injured. Current examples are Raonic, Edmund, Thiem, even Murray who had shingles. The ATP has the resources to review this and in the interests of the players well being, the tennis audience and the overall game I think they should do so.
So you are suggesting to use two years instead of one for ranking points. You´re in good company on this (Nadal), even if I not agree. So in fact you are not criticizing the system, but rather want to change one parameter of it, incidentally the most important one -- which by the way is completely arbitrary.
I am afraid you want to correct one problem (number of matches played) with the wrong tool. The rankings are there to give an assessment of the player´s levels, not to control how much they play. I understand your reasoning, sure, but it could even backfire: being more difficult to move up, some players could play even more...
But you are completely right that the RS influences how much people play. In fact there is already a mechanism on the ranking system that helps on this case, as only the player´s best 18 results (or some other number), count. Considering that, going for two years could indeed make things worst (but that is debatable, sure).
What I don´t like about the two years idea is that it can be easily outdated. Djokovic would yet be a distant #1, and he is not the player to beat for months. If you look, most times the #1 spot changed hands in the last ten years, it really marked the dethroning of a king.