The best alternatives to Next Meeting are Superpowered, Itsycal, and WorkLife. If these 3 options don't work for you, we've listed a few more alternatives below.
What do you think of Next Meeting?
General Collaboration— One inbox for all your work discussions
Itsycal is a tiny menu bar calendar. If you want, it will display your events as a companion to the Mac Calendar app. Itsycal has Dark Mode, ISO week numbers, a customizable system clock replacement, and more.
MeetingBar shows your calendar events in the status bar. Create and join meetings with one click. ⠀⠀⠀⠀⠀⠀⠀⠀ No data or personal information collection. The app is entirely free and powered by an open-source community. ⠀⠀⠀⠀⠀⠀⠀⠀⠀ Works with 30+ meeting services.
Willed Calendar allows you to use the system's calendar and reminders in one app, as well as project management (view progress and add subtasks), event planning, chart summary and other useful features, is a great tool for your management time.