It isn't true, Lewa is a clinical finisher usually. When we check his stats on whoscored he isn't as bad as you say, don't exagerrate.
Robert Lewandowski statistics – 35 years_old Barcelona Forward. Check out his latest detailed stats including goals, assists, strengths & weaknesses and match ratings.
www.whoscored.com
I think those stats tell which kind of striker he is, a great striker. And not sure Kane is a better finisher.
On what basis do you think Lewa has better finishing? Looking at the stats goals per game? These statistics depend very much on the class of the team in which you play. It is simple - if you have 10 lottery tickets you have a better chance of winning than if you have one. Kane is a machine, last season he scored 30 goals from 21.5 xg in the toughest league in the world. The guy is extremely even-keeled and never goes below a certain level. There have been Lewa's seasons like 18-19, when he scored "only" 22 goals from 30.7 (72% efficiency) and at WC/EC tournaments he is even worse in this respect.
Both statistics:
Here is a comparison of Lewa's best season at Bayern vs Kane's current. Same league, same club, almost the same teammates, both in their prime - you can judge which one performs better under the same conditions.
BTW. Sofascore does not give lewandowski's xG/xA stats from that season. They looked as follows: 31.3 xG (1.14/90), 4.7 xA (0.17/90), Here I have to praise Lewandowski for his efficiency - 131% (120%+ in long term is top class). Unquestionably the best season of his career.