Good question. AFAIK inactive accounts are not removed, after all, the game is playable without paying and players have been known to come back after a "long" time (think 1-2 years, for example when you have a kid).
But, the level a player has reach (on which the ranking is based) deterioates slowly over time when no new ranked games are played. For example, I didn't play rated games for a period of around 2 month (middle of October 2019 to slightly after the middle of December) and I lost roughly 1 level in that time (and most probably also lots of ranking positions). But that is usually 'regained' rather quickly when you start to play rated games again. Details can be found here
in this forum.
But ultmately, I can't say how many players with rated games there are, how many of them just played 5 games and never returned, or how many players played rated games last year, or anything similar.
A better way to compare yourself is the level. New players start slightly below 40. If they play a bit, even if they win/loose half of the time, they'll raise up to around level 40 (because the game sees how they play and reduces the uncertainty about them). The absolute top players are around level 65, level 60 are still excellent players. Players above level 50 are said to understand mostly what the game is about on a strategic level, though they may lack in the execution of their plans or misjudge a kingdom.