Many of the points are more related with implementation than with Teams.

External users and organisation federation is something that is part of on Teams and Slack only realized the need for that really late.

The comments you made on Teams could easily be made in relation to the clunky Slack UX.

30% of the workforce might have some form of disability.

Imagine that you have to collaborate with colleagues who are visually impaired, hearing impaired, colour blind, neurodiverse or with other disabilities. You might have to return back to Teams to be able to collaborate with them.