Office 365 is so much more than just SharePoint. SharePoint still is at the core of everything and intranets and team sites can still be built as they always have been in SharePoint: by centrally creating site collections for different purposes. While this has still been and still is the chosen path by many companies, there is so much more to SharePoint and team work today, that it really should be considered in each and any organization instead of locking the usage to "the way it's always been".
The Office 365 tool pallette revolving around SharePoint today includes:
- Classic SharePoint sites - publishing, teams, blogs, project etc. "managed" site collection created either in Admin Portal by SharePoint global admins or usually offered to users via a site provisioning tool connected to a site order form
- Modern SharePoint sites - two types of sites: Team sites and Communication sites, which users can create using the self service site creation on the "SharePoint" page in O365 portal
- Office 365 groups - "AD groups" created by users; users have shared mailbox and calendar and group site (modern)
- Forms - app for creating polls, feedback forms etc.
- PowerApps - tool for creating interactive apps and modifying list forms
- Flow - app for workflows
- Power BI - app for all kinds of data
- Planner - Microsoft's answer to Trello, ie. canban board app connected to groups
- Teams - app for team/topic conversations; connected to groups
- Yammer - app for conversations
And more, but these are the most essential ones for modern team work, when we are looking at things from a SharePoint perspective. It is no wonder then, that so many times people are totally confused and lost in the jungle of possibilities.
The above mentioned set of tools is more or less loosely connected to SharePoint but not necessarily immediately. Some of them can be used, or rather launched from SharePoint sites, e.g. Flow and PowerApps from a list or library page. Some of them provide a means to show data in a SharePoint page, e.g. Forms and Power BI. Some of them are linked to groups, like e.g. Planner and Teams, and a group also always has its own modern team site with (almost) all SharePoint functionalities.
Modern Team sites however are only one type of SharePoint sites currently available. Modern Commucation sites are the modern version of classic publishing sites. Classic sites - publishing and teams - still exist also. A classic team site (site collection) can be groupified (soon) thus creating a "O365 group wrapper" around it, bringing the group functionalities to it.
In the world of modern intranets, there still are fully branded classic publishing site intranets, but also ones built using Communication sites only are quite a few already. Communication site intranets can be built either by creating subsites (like in the classic version) or in the future by using SharePoint Hub sites (currently available in targeted release) to network separate sites together into a more flexible web.
Since pictures usually say things better than a million words, I will let my little diagram do the rest of the explaining. Hope it helps to understand the different philosophies and technologies behind the different site types!