This is tough… not sure anything will give you everything you want. For me, I use (and pay for) Fastmail and have recently learned just how good their calendar app is. You can use their app or site, or hook up Fantastical or anything else that reads a calendar feed. I think their email app (and service) is excellent and worth paying for. https://www.fastmail.com/
If you are a roll-your-own person, you could install and maintain a NextCloud server. See https://apps.nextcloud.com/apps/calendar and https://nextcloud.com/athome/ this is not for the faint of heart.