That should be up to each user to decide but as always Mircrosoft knows better than you what's best for you. This "new Outlook" is actually a web-wrapper from Outlook.com running in Edge - you will have to use Edge and you will have to be logged in to Microsoft account - this is most likely the reason why they're doing it.
I am growing very concerned with what it means that all of these large tech companies are willing to burn consumer good-will by making these wildly unpopular and barely justified decisions. Seems like each of the top 20 companies on the NASDAQ have made some kind of crazy unpopular change to their service in the last 6 months.
Fingers crossed that these changes will spur more people to invest into switching to open sourced software options.
An oddity that has been around for a while. It was a fairly simple client on Windows 10 too. We used to use it for my mum to access her Gmail as it was so simple.
Moving from a local client to a Web based client is all about moving windows and it's software to a cloud based service. For that to work all your data needs to be remote in the cloud too. This is about what is good for Microsoft, not it's users.
For those wondering about their add-ins, Microsoft quote "To provide a more reliable and stable add-in experience, VSTO and COM add-ins aren't supported in the new Outlook on Windows. To ensure your add-in continues to work in the new Outlook on Windows, you must migrate your VSTO or COM add-in to an Outlook web add-in."
Looks like it might be a while until businesses move to this web based version then, as many rely on business extensions in Outlook.
I hope they make the outlook notifications have the same buttons as the mail app. When I tried the outlook app last time the notifications didn't have an archive or delete button. For me that was the most frequently used button in the entire program.
I use the Mail app on Windows to connect to my self-hosted email. On Outlook PWA, if you don't have an account on Outlook or Gmail then you're out of luck. If the switch actually happens, I'll have to start using Thunderbird as my main app - which still doesn't quite integrate with Windows on boot.