'Fabulous' isnt a word that you can use here - he cost £75m. No one's expecting Messi or Ronaldo levels from him, but his inability to contribute to our general attacking play isnt good enough for the price we paid. You can't just be a poacher anymore to play striker at the top teams - look at what Barca, Real, Bayern, PSG expect from their strikers. Pep even has reservations about Aguero's ability to contribute, and the guy has more goals than Lukaku.
Here's some perspective:
Mo Salah - 26 goals/9 assists
Firmino - 19 goals/10 assists
Sterling - 19 goals/10 assists
Salah and Firmino cost less than Lukaku combined, and none of them are actually strikers. Kane showed on Wednesday how a striker should lead the line. Defender's should be worried by a striker's presence, but Lukaku doesnt instill that because defenders know he takes an age to control the ball, giving them a chance to intercept, he's not particularly good in the air, so they can win headers against him, and he barely uses his physical advantage, so they dont have to worry about trying to get in a tussle with him. Drogba's a good comparator - he was never a prolific goalscorer, but a nightmare for defenders, and one of the reasons Lampard got so many goals (it usually took two defenders to deal with Drogba).