I have a 3.1 system and it's still terrible on many movies made after 2010ish.

P.S.

Even properly mastered content will not work well in a noisy environment (e.g. a car or if you have a dozen fans going because it's summer). Here's my ffmpeg filter for such situations (including a stereo downmix, for those without a center channel):

   aformat=channel_layouts=stereo, compand=0 0:1 1:-90/-900 -70/-70 -30/-9 0/-3:6:0:0:0

No: The problem is directors who love mumbling, audio people who have no idea how to record and balance audio properly, and media players that can't or aren't configured to properly downmix audio tracks as appropriate.

It is absolutely possible and honestly standard fare to have properly balanced audio playing on the $1 tin cans found in TVs and laptops.

No, you'd be surprised at all the random crap they put on the center channel nowadays. You just need an equalizer and use it to boost the frequencies of human speech. A lot of AVRs call this "dialogue enchancer", but you can do it easily in software