I'm absolutely baffled by colleague who somehow manage to be five minutes late to an online meeting while working from home. Because you're right, you get a reminder 10 - 15 minutes in advance, you just need to click the join meeting button, you're already at the computer. We have, for remote meetings, a five minute buffer at the start of every meeting, for people to "settle in" makes no sense, just start the meeting.

In general a lot of people just aren't being serious about meetings, which I guess is also why many hate them. So key indicators of a bad meeting is: runs more than 60 minutes, no meeting plan, documents or talking points provided in advance, more than five people (unless the meeting is more of a briefing).