This is the first time I've even heard people in public actually say that the current playoff structure is bad or boring at all hence why we haven't even considered on any change yet beforehand, but I do agree with the points you've listed here except for the double elimination itself, but I'm not exactly defending it either.
Pretty sure the implementation of the Double elimination in the first place was done to make the playoffs less anti-climatic where the 1st seed team was already a guaranteed winner pretty much (duh) regardless of the 2nd/3rd seed team having just battled out for a spot in the grand finals and being as warm as they could be, can't remember these things exactly from 3 years back. However I do agree that the current format does drag on for too long and changing up things for it would make things at least a bit more fresh so the playoffs won't need to last for 3+ weeks.
zxpThis format leaves more room for upsets, like in season 28 where the fourth place seed Ascent.EU beat Lowpander and Lego and ran Svift really close in the grand finals. Although I realize thats rare, imo thats worth the delay.
Something that could work in place of this would be to have a playoff structure similar to Season 23 instead of Season 21, where 4th seed team was also taken into the playoffs and had to play their match before the semi-finals and grand finals, in which case the 4th seed team won the 3rd seed in this example. I'm aware however that this can't happen in every season and this was also the only one where this did happen with single elimination.