Center channel downmix boost or something is the name. Iirc the phenomenon with quiet dialogue is due to most streaming content being delivered with surround audio. The shitty cheap video players used by the streaming services will do a cheap flat downmix to stereo which results in the center channel being too low when split into two mono channels for playback on stereo speakers compared to if it would be played on a dedicated center speaker. This is due to maths or something.

Back in the day dvd and even vhs movies had proper stereo mixes where the center channel would be boosted to audible levels.

Tl;dr: just pirate shit and use a proper video player instead of the cheapass players used by netflix, disney, etc.