I'm ok with single elimination games; you get fluke results in the NFL & NCAAs with them as well, but, that's sports. Show up on the day and win. Simple.
I'd just like it to be that the higher seed hosts, and rather than away goals or PKs, if the game ends in a tie then the higher seed advances as well so it puts more of an emphasis on the regular season. I don't think they'll go to that, but it makes sense. It may lead the home team to bunker, but if you play for a tie at home but give up a fluke goal in the 89' on a bad backpass, well, you're fucked, so good luck with that. Making the away team play to win rather than bunker for PKs would be good motivation.
The first Seattle-TFC cup final in (iirc) '16 was an awful 120', with SEA basically playing for PKs and TFC unable to score. With a one game playoff on the road, you could see a lot of the earlier rounds going that way as well; having the higher seed advance removes that as a tactical option, the away team has to come out to win. The away team pushing forward should give the home team opportunities to counter, and maybe now you've got a game. If it turns into a 0-0 suckfest where no one scores, then at least you've given the team that had the best regular season a reward for that effort over a 7+ month season.
MLS won't do that because they enjoy the drama of PKs for the sake of television, but I'm ok with that format up to & including MLS Cup. Why should 7 months of effort come down to PKs in the final either, if it comes to that. Regular season matters, make the higher seed the winner of any playoff game that ends in a draw, and fuck the PKs. You'd be setting up for drama at the end of 90', instead of two teams playing ultra conservative in 80'-90', then remaining conservative in 90'-120', and playing for PKs in extra time because they were too tired.
The only spot where it's really a problem is when two teams are tied on points, like the 2 seed in the playoffs makes it from each conference & they are tied at 65 points each. You wouldn't want the 5th tie-breaker deciding a tie game for the title, etc. You could make the first tie-breaker wins, and then only go to PKs in the very rare instance where both teams were tied on points & wins AND the cup final game ended in a draw, which would make PKs pretty rare.