I agree that it's too easy to just blame avoidance. For me there is a very viscerally different feeling when I'm avoiding something because I really don't want to do it, vs. when there are other things I want to do because they're entertaining.
The difference is that if I genuinely have other things I want to do, I'll get enjoyment out of it, while if I'm trying to avoid something else I'll get to a point where I'll think "hold on; why am I doing this? I'm not enjoying this" and realise I'm doing it to avoid something else, and still feel the pull to do some nonsense activity while getting more and more miserable.
One strategy I've used is to try to stop regularly and simply ask myself "am I actually enjoying this? why am I doing it?" - I give myself relatively wide latitude to continue "wasting" time if I'm actually enjoying what I'm doing, because sooner or later I'm "done", and if I was actually myself I often feel energised enough to get much more done afterwards.
But the moment I'm not enjoying myself, I'll start probing into why I feel that way.
Some of it certainly fits under "avoidance", but that's also a very broad category and not very useful without exploring the more specific reasons I'm avoiding things.
Sometimes it's because it's too much to bite over, so I instead "procrastinate" by deciding to break down my todo list into smaller chunks. Often that will break the deadlock by identifying small-enough tasks that I'll be happy to get out of the way (I guess that fits into your "micro-todos").
Sometimes it's just not a fun task, and I'm pushing it ahead of me because I know my self-imposed deadline is not real and is just waiting until I really have to do it. In which case I'll try to reorganise things and do something else instead and just accept my tendency to do things right before a deadline when I know how long it'll take.
Sometimes I'm just too tired, in which case I either go rest or try to pick activities I can do while tired (benefit of working from home: if I'm mentally worn out, there's always housework to get out of the way which doesn't require much thinking).
Sometimes I "trick" myself into it by setting a schedule of 30-60 minutes of different sets of tasks. So I'll commit to "only" doing 30 minutes of what I need to get done, then maybe an hour of something lower priority that I actually enjoy, then another hour of my urgent tasks. Sometimes I'll find when I've just tricked myself into starting, I'll keep going longer than scheduled, if so I'll let it happen, but if not I'll strictly adhere to the limit on the more enjoyable tasks and keep track of whether or not I start lagging behind my schedule.
Sometimes the things I've decided logically I "should" be doing just don't emotionally feel like a good way to spend my time. E.g. I might have decided I "should" be planning some new project because I think it's important, but emotionally I might be drained and need downtime, and dragging my heels is a way of not having to acknowledge I have too much on my plate.
For things like Reddit, I find a major factor is the inbox. If someone replies, and I read their reply chances are I'll compulsively reply. This is easier to avoid with HN. With Reddit, what helped immensely was when I recognised what I was doing, and every now and again go "ok, enough" and click the inbox and physically look away until I've gone back to the main page to get the unread messages safely out of the way without having them draw me in again. Making it less intensive by cutting off heated arguments that way makes it much easier for me to break away and do something else.