Since I use the calendar for my shift schedule (which consists of both recurring and one-time appointments that can span both single and multiple days) the multi-day events are more important to me and I need them to have a colored background box. While the old calendar could use a dedicated shift feature, the colored background box for multi-day events was decently useful. Having that replaced with the thin dotted lines makes it really bad for this purpose.
For other people, though, things might be different. Why not give us the option to choose whether we want solid background colors for full-day (or multi-day) events, and colored text for shorter events, or vice versa?
Thank you for your feedback! We have just released an option to switch to more saturated calendar colors in the new Outlook.
If you would like to try out this experience, please click on the gear icon in the top right of your calendar module to access your settings, and toggle “Bold event colors”.