It happens sometimes in Star Trek that the quality of video chats is too bad. Why don't they switch to audio or text only? This would save bandwidth and they would communicate better.
People don't switch to text communication because they prefer video, even when the video is of low quality.
We know that text communication is possible, because the bridge receives messages without using the screen from time to time. For example, there is the time that the Enterprise D received 285,000 hails at once from Enterprises from parallel universes.
So why don't ships in Starfleet use this method of communication more often?
This could be a matter of personal preference for Starfleet officers. In Star Trek, video communication is ubiquitous. People grew up with it. It's fast and almost always reliable over vast distances. In the rare situation where the video starts to break up, it would be more efficient to switch to text communication, but people aren't used to doing that. Instead, they keep using their video screen, repeating themselves as necessary.
It's a bit like trying to talk to someone in person in a noisy environment: if you both have phones or something to write on, it would be simpler to communicate via text, but it's common to simply raise your voice and repeat yourself as necessary. In Starfleet, even when text communication would be more efficient, everyone expects to use video, and so they stick with it. If it works at all, people will use it.
Presumably, if the video and audio cut out entirely and can't be reestablished, people would switch to text communication. I can't think of any examples of this happening at the moment. Also, if video and audio communication is impossible, there is probably an emergency situation in progress, so the crew needs to focus on correcting the situation, possibly neglecting to maintain text communication with other ships.
You’re assuming that the video connection quality is bad because of lack of bandwidth.
It’s possible that within the universe of the show, the bad quality is actually because of interference with whatever signals are being transmitted between the ships, and that this interference would still cause problems for text- or audio-only transmissions.
Or maybe the universal translator only works with audio.