Wow, this is quite shocking. I used to work in Amsterdam and Miro used to be one of more well-known companies there. A few of my friends worked there at some point.
I used it quite heavily at one company. I found it a bit bloated, but it was ok, and I didn't have to jump between one tool and another, it allowed me to draw some diagrams, do retrospective, share ideas with others.
Clearly the pandemic skyrocketed their valuation to a level they couldn't maintain...