I've mostly stopped reading technical mailing lists
Once upon a time, I subscribed to and read a lot of mailing lists for the software we used, things like Exim, Dovecot, Prometheus, ZFS, OmniOS, and so on. These days I've mostly stopped, which is a shift that makes me a bit sad. Technically I'm still subscribed to some of these mailing lists, but in practice all their incoming messages get filed away to a folder and periodically I throw out the accumulated contents and start again. These days I only read one of these mailing lists on the rare occasion when I'm asking a question on it
Some of this is because my interests and available time have shifted. It no longer feels so interesting and compelling to keep up with these mailing lists, so I don't; usually I feel I have better things to do than to slog through any of them. But that 'slog through' phrasing is a clue to another reason, where reading some of these lists doesn't feel as productive or engaging as it used to. It's not all of the mailing lists; some of them simply have more volume than I have time and enthusiasm for, with not enough important information. But with some mailing lists, it feels like the character of them has changed over time to one that is significantly less useful to me.
(To some extent I expect all technical mailing lists to get less useful for me over time. In the beginning I'm relatively new to the software and so I can learn a lot from listening in on ongoing discussions and hearing routine questions and answers. As I become more experienced in whatever it is, more and more of the messages are about things I already know and the nuggets of new information are increasingly rare.)
The primary change I've noticed of these mailing lists is that they see a lot more questions that are either basic or very specific, where if I had the question I would have expected to answer it myself by reading through the documentation. In the beginning I had unkind descriptions of these sorts of questions, but I've come to be more sympathetic to them, especially the questions that come from people abroad who may not have English as their first language. The unfortunate fact is that projects aren't necessarily well documented and their documentation probably is dauntingly hard to read for people who aren't fluent in technical English, and people have work to get done (using those projects). Turning to the project user mailing list and asking their questions, if it works, is probably much faster than the alternatives (and their boss may be yelling at them to get it done ASAP).
This is, unfortunately, where the differences between mailing lists and forums become pointedly relevant to my experiences with mailing lists. My current mail reading environment is not well suited to situations where a large amount of the volume is uninteresting to me and I'm picking through it for the small number of interesting discussions of interesting issues. In a forum, I could ignore entire topic areas and most of the threads, focusing only on some specific ones of interests; in my current mailing list environment, I drown and stop reading.
I could likely manage to do better with various alternative ways of following these mailing lists. But although I kind of miss being the sort of person who reads mailing lists for software I use (and tries to write helpful responses), the amount of value I might get out of doing this has so far felt too low to motivate me to do anything. Just not reading things is easier and I'm probably not missing much.
(Pragmatically, some software I use has forums instead of mailing lists and I don't try to follow those either. As much as I would like it to be otherwise, I think my interests and enthusiasms have shifted significantly from the past. Am I burned out on the whole 'mailing list/forum' thing? Maybe.)