You can try Kodi with add-ons for those services. It's a bit of work to get running, but yeah. You can play with volume amplification.
The only solution AFAIK is to run these apps via Kodi. The Kodi player has a demix option in the audio settings within the video player. Increase the slider to +6 or so to get great volume on dialogues (it basically boosts center channel volume).
Some tvs have a dialogue boost. If you have a receiver, run a centre channel speaker. You can alsoblook for loudness mode or midnight mode on your avr. If your tv has an equalizer boost 3000hz range. 1-4khz is the human voice range. Shut maybe there Is an android equalizer app.