That is pretty well said. Worth noticing though, that it is the Grealish fanboys and/or Strerling haters that bring Jack into the conversation, as some stick to beat Sterling with when they run out of shit to pile on him.
Which then descends into said whataboutery as he has been totally filicking invisible for a whole season. It's quite a handy thing, argue Sterling is leaving because he has been replaced with a better player in Jack, but dare you compare the two, then it's hey they are completely different players (which they obviously are).
At the end of the day, Sterling has been fantastic for us overall. And he's made the club a marginal profit on top of that. Grealish has a long long way to go to even begin to match that contribution, however you want to measure it. Wish he does, we'd all be delighted, but that doesn't have to come with belittling Sterling's achievements here.