Someone would send you a document and it took over the entire Teams window. You had to exit it in order to chat with the person about the document. The concept of having more than one 'thing' on screen at the time was completely missing. My only explanation was that the developers had never used a computer before.
Try not to blame the people working at the coal face. Developers lack influence in most companies, they are told what to do by product managers and the rot often gets worse further up the hierarchy chain. Developers mostly know what is wrong and don't like the shit they are doing. Imagine the anger of working on Server 2012 (Windows Server 8) with the default Metro UI - that idiocy had to go right to the top.
How independent are developers at Microsoft - are they in charge of product design decisions?