We need to find some balance.
Some members have been spot on regarding what adding Lukaku would do to the team. In this current system, we aren't creating that much with Lukaku up top as opposed to the interchangeable front 3 we had.
433 would work against some sides but we are still incredibly weak in defensive transition given the lack of quality in the DM department. We also don't know if Rudiger, Christensen, Chalobah can perform at their same level in a regular back 4.