With the current conditions, the higher score will slowly grow indefinitely if there is enough activity
it seems that there is an inflation of score points in the top league, maybe due to points taken from players joining the top league, losing points and then stopping playing or going back to lower leagues. In this way (at glance, it has to be formalized a bit better) the top league is slowly accumulating more and more points that then end up on the top players (especially if those do not get inactive for long time).
The phenomena is balanced only when top players (top league) stop playing, making points not accessible to others (because there is no exchange of points with those players).
Once reaching 1700 points was difficult, then reaching 1800 points was difficult, then will be 1900 and so on. Unless, as written above, top players go inactive and the points gained are removed from the pool of points exchanged. The same would happen if a lot of players over 1000 (the starting score) gets inactive, they will retain more and more points out of the pool of points getting exchanged.
So saying that a player with 1900 points is stronger than one that had 1600 points some weeks ago is likely a wrong assertion.
See also: viewtopic.php?f=5&t=9&p=5225#p5225
Comparing historical scores
One could say "ok, so how can I compare players according to historical scores?".
Well if we want to be pedantic, one cannot compare scores because those were achieved in certain conditions that are not repeated. One should provide the same opponents, the same level of skill for every opponent, the same type of AI controls, and so on. Too complicated.
But then could we approximate and say that a 1600 score now is equal to a 1600 score in 3 week in the future or 3 weeks in the past? No. It depends, accepting approximation, to the rest of the scores assuming that the score formula does not change . If a 1600 score was in the past (3 weeks ago) a score held for a couple of games in the top league by the top player, while in the future (3 weeks from now) a 1600 score is the score normally held by players between the position 10 and 15, surely a score of 1600 was way more prestigious in the past than in the future. So relatively to the opponents active at that time, a 1600 in the past is way more stronger than a 1600 in the future.
But then we cannot compare at all? No we can still compare, but not at glance. Thanks to the score formula (see ) one could compute what a player could get with a certain score against his opponents at that time.
For example if in november 2016 a 1600 score player in the top league, winning the other players in the top20 could have get on average between 8 and 5 points, it means that the distance between the players was quite large and so the player was dominating. Instead if in january 2017 a player with 1600 score in the top league would get between 10 and 25 points from the top20, it means that the player is not weak but neither dominating. Actually he has often many over than him.
The problem is to get a "snapshot" of the ranking at a certain time (I'm doing this on telegram with screenshots), since mostly one can see the historical elo of one players, but not how strong was this score compared to the other players at that time.
Example from the telegram chat
TCT around 2200 is outstanding
you're right that the ELO is fine now that I stopped to think about it.
He's ~8% ahead of the 2nd and is not losing many points with a loss, which is correct if look at the past.
Not that his score is not outstanding, but I was twice as higher than the 2nd (14%) back when I was playing hours in a row, which would be the equivalent of 2500 today and each loss would take between 20-30 (more than 1% of all my points) points from me, while today he loses 0.5%-0.8%.
So yes, I think the ELO is working fine
Hmm two flaws of your argument if I'm not mistaken. First you talk about percentages, that are wrong because the score is limited by matchmaking and elo formula. So you should account in terms of 'percentage of predicted success by the score formula' if you want to compare apples to apples. Percentages makes sense in other context. Again a confusion with the score model.
If you have 200 points and the second has 100,you have 100% more points, but the predicted winning percentage with the score formula is lower compared to someone that has 2200 and the second is 2000. Because what matters is the delta not the percentage. This is a confusion in using percentages. If I have 0 euro and I get 1, my improvement is outstanding in percentage terms, even compared to the one that had 1000 euro and ended with 5 gazillion.
As a reminder: smaller numbers, same delta, bigger percentage. Higher numbers, same delta, smaller percentage. Due to the score model, what counts is the delta.
Said that, tct has an outstanding score.
Second it depends how active were you at that time. When was that?
Further explanation: viewtopic.php?f=7&t=472
 the score formula should stays the same (because it can be tweaked and was already changed, see kfactor, halving points after draws [source on the old forum], etc.).