Blame your TV, not the content. Or, blame yourself if you like for not buying a soundbar or soundsystem.

A lot of TVs these days have Night Mode or the like. That's the fix!

PS Downvoting me for... What exactly? Because I told you two solutions and neither of them are what you prefer? TVs are literally paper thin and physically can't have good speakers except for special cases in the high end. Buy a soundbar, even though they suck and apparently people these days are scared of plugging one more cable into something, or get a stereo system for the same price and plug in two more things (speakers) that can fit anywhere on your wall or whatever.