Timer is fun as a one off challenge, like the MOP challenge modes. But they intend m+ to be the primary form of progression for players who can't raid, and it's not fun for every single run you do to be a timed run where a wipe at the wrong time ruins the whole thing.
It was also more fun during legion before the community optimized it. In Legion you could go in and just kinda do your thing and not be super worried about exactly hitting 100%. But by BFA it was already over. I was pugging in the second week of BFA, before m+ was even released, and I had people complaining that I wasn't optimizing the route and skipping skippable trash packs. Literally my second run ever in the dungeon. And it hasn't gotten better - last season's affix with the precise timing for each miniboss just made it worse.