Need to ? Kind of, but it depends on the context
Would it be good ? Yea, ideally we need roughly another 15 goals a season over and above what we're likely to score this season. It doesn't really matter where those goals come from, but they'd be likely to turn a few draws into wins. If scoring that number of goals brings down Lukaku's percentage, which it almost certainly would, then job done.
Probably a more pressing issue is to have someone available how can play up front instead of Lukaku now and then, or come off the bench to replace him on his off days. If that someone's capable of chipping in ten goals a season, then we're well on the way to pushing for top four. Finding someone who's good enough to do that and is happy to play second fiddle to Rom is a nightmare though.