He reminds me of Sterling because they were both a split second too long on deciding to shoot or pass too often but there's a big difference between the two. When Sterling got it right he scored and assisted plenty and was a game changer, Grealish has not scored or assisted anywhere near enough and has very rarely been a game changer, that's the difference.
He's played LMF twice recently and it's obvious he isn't good enough. He thinks too slow, runs too slow, his off ball positioning to receive the ball isn't good enough. When he gets the ball he looks to get rid soon as possible playing short easy passes, often backwards. He lacks energy drive and pace (he had when at Villa) His shooting is usually piss poor, that's when he gets in a good enough position to shoot.
He's been underwhelming and average most of the time, especially for a player costing 100M. And mentioning the fee does matter because it's a huge amount to pay for show pony that's failed to live up to expectations.