I thought looking at an older game might be instructive with respect to the decline of games over time.
Planetside II can be seen very much as a spiritual successor to the Tribes franchise, released by SOE back in Nov 2012. It’s a game which never really got much exposure but maintained a loyal core following over the intervening years.
The PC version of the game is available either stand-alone or though steam, so the numbers reported by steam charts is not representative of its actual player counts showing Steam only, but the movement in player count probably tracks well.
The following graph shows the player count over the intervening years, with the dramatic drop-off at the start and a largely stable if waning player count in the following years.
This slow decline in player count can be seen in the numbers for the more recent months, showing a game clearly still pulling some new players to replace those who leave. But unfortunately not quite in numbers to reverse the overall slow decline.