You are wrong and I think Lukaku had a good performance in the last games of the previous season we saw, however, because of his age they can't count on this player as a long-term plan but I think Lukaku could even have a better performance if he didn't get injured because Lukaku helped Inter Milan a lot in the champions league and he likes to play in this team that's why I think investing on Lukaku is not a bad move.
After seeing Lukaku performance in his first season with Inter Milan last season I think he has made a big contribution to Inter Milan. I think that Inter Milan will continue to try to use his contribution again for next season. Even in Fabrizio Romano tweet where he said that Inter Milan had already negotiated with Chelsea to be able to borrow Lukaku with several important points in this second agreement.
Even though they have succeeded in bringing in Thuram this season, Inter Milan still wants to get an injection of energy from Lukaku for next season. Indeed, statistically Lukaku where he suffered a setback compared to the season before he moved to Chelsea. But inter milan is his home and i'm sure he will be able to develop well in the next season if inter milan lends him again.