If that's not the case, are you really sure that you need to be doing any of that? Especially "get a word in on something important" is awfully similar to https://www.xkcd.com/386/ .
Dedicating a time slot in the usual sense is very socially costly if they've gravitated to a presenceless, fast-moving platform, because psychological consensus and topic closure operates more on the perceived speed of communication of the group. If 90% of the other people respond within an hour, and you get there eight hours later, the conversation's moved on, so if everyone else is in the habit of checking their phone every fifteen minutes, there's pressure for you to be too. So, yes, you can “dedicate a time slot” at the end of every pomodoro, if that's what you meant.
This is more true in “channel”-based environments where “new in thread” is inconvenient or unavailable. If you're not careful, you can even be disruptive. Even on slow-moving, old-style Web forums, “necroposting” is considered rude; a chat-like medium with little to no threading support can just lower the threshold for it from weeks to hours if there's enough activity.
For the other part, I'll grant that “get a word in on something important” was badly worded, though I can't think of a better phrase this instant. I was imagining things like “we've changed the meetup location because someone raised a problem, is this okay with everyone or does someone need a ride” or “I'd like comments on which direction I should go with the next part of this piece” or “I'm going to see if some of us can do X together tomorrow, I want three more people, who's with me”. All of these can easily render your participation irrelevant if you show up too late, and “too late” is by default defined by what's usual and convenient, not by abstract considerations of what's good for people's habit formation.
If they're doing it only because they kind of fell into it as baseline socialization shifted, they need to step back and reconsider things because it's not healthy.