My perspective is a little different:
I believe the nil is what keeps luck from dominating. If nil is forbidden, the team that's dealt more spades and high cards will win, most of the time. Bids will be higher becasue there is no need to underbid to discourage oppos from nilling.
I'd expect the game to resemble mirrors, basically. The bidding a bit more rational, obviously, but still I'd think we'd see 11-13 bid every hand.
What I like about nils is that they are equalizers: if your oppos get all the cards, you can stay in the game with nils. Snd there's a LOT of skill in bidding/playing nils. I'm sure y'all have noticed that the strong teams bid and make more nils than the weak ones do.
Not to mention the sheer, illicit thrill of holding 2 aces and 2 kings and bidding and making nil.
I'd be in favor of a format that forbids dnil, as a variation, more than of one that forbids all nils.