Basically, in both cases (computer/app or dial-in), increasing the number of digits of the meeting ID has very little impact on the users. Forcing a user to enter a password after joining (which is just more digits) does impact the user.
It is a frequent use-case that people join meetings from devices that are not running a calendar application, or the calendar does not have the meeting invite.
For example: conference rooms.
The situations and use-cases behind meeting-software are such that you can't rely on this.
There are many situations where you want to transcribe the information. For example, dialing in as voice-only with a private phone based on an e-mail on your work-laptop.
Or perhaps a conference room at a client-site where the client-guy has their corporate-approved presentation laptop, but he can't find the e-mail/chat message with it. Meanwhile you've got it up on-screen, but your device is not approved for any kind of internet connection in this part of the labs, and even your phone has no signal. (Yes, I've been there.)
I generally like the idea of smartcards, or having some physical thing you carry around which is used to authenticate with systems.
I think focusing on "relative usability" is important too. IMO it should be able to increase relative usability AND security.
For instance, I find unlocking my phone and paying with apple pay is easier to use than taking out my wallet and paying with a card. Having my credit card information encrypted on the phone makes it harder for a thief to access, when compared to gaining physical access to the credit card.
I also use a yuibkey to store cryptographic secrets. Generally I leave it plugged into my laptop, so it does not add inconvenience to me in using it. Before I had to type in a long password to decrypt my SSH key. Now it's stored on a YubiKey, protected by a shorter PIN, and requires a physical touch to perform cryptographic operations. By moving cryptographic secrets from a system with a large attack service (the laptop) to a device which requires physical access and has a smaller attack service(the yubikey), I find the system is easier to use, while increasing security.
One could argue a lack of security can lead to a decreases usability. Ex, a system under a successful DoS attack makes the system not very useable. I digress though, as I do not believe this is what you were getting at.
Also create dud rooms with prerecorded conversation.