+1 from me.

As a visually impaired player it is quite difficult for me to read dialogue during non voice acted scenes and quest dialogue, most of the time I end up just skipping through it as my eyes get easily strained from trying to read small dialogue.

As you've said OP, I am surprised that there is not an option for this considering how much UI customisation is available.

Unfortunately though this is probably not even on the developers radar for things to adjust and with how much dialogue/lore there is in this game it would probably be quite a time consuming adjustment, especially when you have to consider different font sizes scaling in the dialogue box as well as keeping the flow of cutscenes.

Still though I could be overthinking it a little and that it can be a relatively easy adjustment, personally, I would be happy if we could just blow up the size of the dialogue box.

You have my support OP!