For the leagues based on fixed scores it is true. Although with resets and adjustment you can fix it.
In discord people had the idea to take the scores of the previous seasons to set them for the new seasons.
Example in season 1 the 25th place had, say, 1980 points. Then in the new season 1980, or the score of the 25th player (active or not) is the minimum to be a GM.
If seasons are short enough then this method should be quite ok.
Elvenmonky you also miss some understanding how the score formula works. If you do K-factor 20 if one loses and k-factor 18 if one wins, you may have less fast progression towards the top, but the points (defined by the kfactor) are simply exchanged. They are not removed from the game. Also playing with taxes without testing the taxes properly, normally creates more probelms that it resolves. The elo formula is tested over years, a random tax just easily written in English is not.
Then once again, for the simulation I did, the problem of "inflated scores" happens even without ghosts. I let 10 entities play each other for 1800 matches and the strongest one ended up with 4000+ score on an average of 50 runs (so 1800 games x 50 ). (the base score was 1000)
Accumulating score at the top is something that happens, unless everyone has the same skill (and in that case the game would be boring). You cannot avoid it without making the score useless.
I agree on the leagues thresholds, but then I think that using the previous season threshold is a simple change that should work and if it doesn't work is not going to create havoc.
Of course this is true if the seasons happens regularly every 1-2 months (the seasons themselves are quite a tax as they reset the score to the base league score). If not, the idea won't do much.
For example pre reset the top 20 (active or not) had 48355 points. (n1)
Now the top20 (active or not) has: 48876 (this 1 month and 2 days after the reset)
A super close value, so the scores are relatively stable unless one let the system run indefinitely with ghosts + many active players (without active players the points would be frozen).
Also a player has to be stronger than the ghosts to accumulate points (and release ghosts with more points). It is not that trivial.
With this I mean that recurring resets + adjusted league thresholds would fix the perceived problem of "GM league is getting easier". Although the idea that I read here and in discord "ah everyone is a GM now" it is quite a subjective argument. I wouldn't mind having only one league (but with small kfactor, so like 20). Bragging about the league is bragging on epenises, shows little maturity.
(historical data refutes so much easy sentences)