I agree L-canceling is fundamentally stupid, but Melee would not be Melee without it, and I don't think Auto L canceling made Brawl+ any less horrible. Furthermore, while they are very uncommon, there are in fact competitive reasons to miss an L-cancel in Melee. Mostly revolving around how teching works in Melee.
Project M seems alright to me. I don't like the execution adjustment from Melee given minor engine differences from Melee, but I think balance-wise, they're on the right track. I do however personally think Link in the demo is the current worst character. This wouldn't be so much a problem in my book outside of the fact that whoever is running the Project M Dojo doesn't know what they're talking about, especially if they suggest that Project M's Link is competitively going to be the best seen in a Smash game.
If you ask me, BBrawl's Link CRUSHES Project M's Link in terms of competitive viability (heck, I suspect if you actually transferred BBrawl Link's PAC to Project M, he would be a better character specifically because of F-smash and Z-air lol). There's barely a comparison. I don't know if you've kept up with the Dojo site for Project M like I have, but I definitely have issues with a lot of the things they suggest.