Because, IMO:
1. PP with Carlson is just as effective as with Green, so there's 16 (of current 36) Green points you can simply replace.
2. Without PP, Green is what, a 25 pt guy? A 30 pt guy? If you drop off to a 15-20 pt 3rd pair guy, that's only maybe a 10-15 pt difference.
3. With Green gone, you'll likely allow fewer goals, fewer dumb unnecessary goals (unlike goals that opponents would score on anybody, these are Green-special back-breaking goals), fewer goals in tight Trotz-type games, etc. Those could easily account for more than the 10-15 pt negative difference.
4. With Green gone, you'll have one less fragile player that is highly questionable to survive a full SC run.
5. Getting a solid top-6 forward would not just mean individual improvement -- it could completely change the effectiveness of the 2nd line and improve the stats of at least 2 other linemates. If you find a forward that clicks with Kuz, you can get two great players.
6. Getting a solid 2nd line would improve the whole team by tilting the ice more, putting more pressure on opponents.
Honestly, I find it incredible that you don't seem to even understand these arguments. I mean, you acknowledge them, but then the next day you come back with same stats-in-a-vacuum, as if Green's positive and negative contributions can even remotely be summarized by reading off regular season point totals.