I've been giving New Outlook a go recently as, despite regular 365 updates, actual fixes to Classic are less common. The most irritating has been a failure to correctly display some emails containing graphics etc e.g. QR codes needing to be scanned, and MailTips disable settings not saving, as examples.
Recently two things were fixed eventually - Event 300 'Failed to parse element: VersionOverride' (after many months) and more recently Copilot (enable/disable now available).
Some things I miss - a new mail envelope in the system tray that can be made visible separate to the Outlook icon, better control over download/display of images. It was a little harder to get an attractive presentation in Windows dark mode - Light and Image worked in the end.
I'd been content to extend a 365 sub to have Outlook Classic as well as Word and Excel, but if New keeps improving then the benefit of the sub becomes questionable.