1) Sakurai has a irrational hatred for competitive games.
2) Brawl air dodge
3) No L-Canceling
4) It`s not being made from scratch, it`s most likely being made off of Brawl`s engine and they copy over returning characters 1:1 from brawl before making changes too them.
5) Why would Sakurai balance patch a game he doesn`t want to be competitive?
Good points, so I'll reply to each in order.
1. I'm not going to argue with this point, but several anti-competitive things like tripping are already gone. While I don't think it will be quite like Melee, at least Sakurai is listening to some of the complaints that people made about brawl
2. I know I'm in a small minority, but I liked Brawl's air dodge. With that said, we have seen little of the air dodge so far. It may not be 100% like Brawl's or could be a mix between Melee and Brawl's airdodge system. As an example, you can dodge a few times int he air, but you forfeit all other moves in exchange. The Brawl airdodge could also simply be a placeholder until the change the air dodge. We just don't know enough about that.
3. Has Sakurai said L-Canceling is not coming back? Unless he says it, we can't be sure at this point if its coming back or not. It could either not be programmed in yet, or the videos are simply not showing it off yet. Unless he says it is not coming back, its too early to know for sure.
4. I would assume the copied Melee's veterans the same way. It does save them time to copy a character, and make the changes. What I meant is that stages, modes, and other things that can't simply be ported from Brawl have to be built from scratch. Plus, even if they did copy the characters they have to adjust the veterans to the new engine. Sakurai has already said that the game is going for a middle road between the speed and gameplay of Brawl and Melee, so I would assume that there is either a new engine being used, or a really modified version of the Brawl one. Even if they copy characters, alot still has to be built from scratch.
5. We don't know that for sure. They do have Namco involved, so there might be patches. Again, nobody knows for sure. Maybe he will patch the game post release to fix bugs or other issues.