iCloud.com behaves this way because you should, theoretically, be able to do everything you need to elsewhere on your device. If you find yourself in a situation where you need to get into your iCloud account through the web, you can still do it by tapping the share button and tapping "Request Desktop Site." This will get you there but it won't be pretty as it isn't optimized for mobile.
HomePod owners already know that Siri can help with a variety of tasks. Asking Siri to deliver the weather forecast, play music, or answer iPhone calls is just the beginning. For anyone using Find My iPhone to track a lost or missing device, Siri on HomePod can help with that, too.
Those who are signed up for Apple's Beta Software Program and testing iOS 12 may have noticed that it offers a new way to share photos - by sharing a direct link to your iCloud Photos that will last for 30 days. Not all features found in beta make it to the official iOS, but hopefully this one will, as it pretty useful for sending multiple photos. Instead of actually attaching each photo to an email or sending them in Messages, you are merely posting a link.
Grouping your contacts makes navigating them on iPhone much easier and allows you to message and email a multitude of contacts at once by allowing you to simply use the name of the group rather than typing in each individual every time. Unfortunately there is no way to do this on the iPhone itself without a third-party app. Apple prefers you to use iCloud to make contact groups which, once you created, will sync across all of your devices. Here's how to make a contact group with iCloud: