Lukaku is arguably in a different league to every other player in world football when it comes to pure goalscoring.
Unfortunately, he's also in a completely different league to top players when it comes to everything that actually makes a top level actual striker. A much lower league.
That's the issue, and that's why Morata is infinitely more appealing to a top club than Lukaku. All top clubs rely on movement and technique first from their strikers, and goals a distant second. That's why Morata is at Real Madrid already, and Lukaku is at Everton.
Because of his goals and, as such, his resultant prestige to his club, Lukaku is overvalued and costs a fortune - in real terms, Lukaku's actual value as a footballer is a fraction of the fee it'd take to get him.