Have you changed your default meeting times to 25 minutes and 50 minutes, instead of half an hour and an hour?

I don't think the length of meetings are as important as having a true timebox and holding one another accountable to that timebox.  This means ensuring nobody takes over the meeting or derails the intent of the meeting.  Meetings should be straight to the point and concise in what they are trying to achieve.  Too many try to have banter or get something addressed that isn't even in the realm of what the meeting is for, and in that case a separate meeting should be setup or just collaborate with communication tools in real time such as slack to avoid meetings altogether.

If people are having too many meetings that seem to go nowhere, there is probably room to utilize communication tools more to knock out a lot of the questions that they are waiting to get to a meeting to ask, this way the meeting becomes more of a review with all stakeholders on what has been determined so far and the focus can be on any further refinement of those points or to get sign off instead of treating meetings like a real time discovery session.

Yes… it is really helpful and MS provided this feature so you can enable it by default

Not yet, but an interesting idea.

25 and 50 minute meetings are nice in theory but most will see them as 30 and 60 minutes. I don't see the need to formally cut them short in planning as the meeting can always end early and people will not typically complain.

Now the opposite would not fly too well if you planned meeting times at 35 and 65 minutes because people would definitely think that was too long.

Yeah! Definitely... This gives you the breathing room from the previous meeting and is self-enforceable.  This is a policy I try to enforce with my teams on every project.  But since covid, it has been especially critical.