If you like Office 2003, then I'll suggest the free Libre Office because the theme looks very similar and it is absolutely kept up-to-date with the latest version being released 5 days ago.
Plenty of people don't like 2007 and later due to the huge ribbon interface that takes up so much screen real estate leaving less for your document. If you get a larger and higher resolution monitor this isn't as much an issue but laptop screen users are kind of stuck. 2003 and earlier all use the same dropdown text menu system everyone was familiar with so changing to the ribbon led to a lot of wasted time looking up how to do things they knew how to do before.
2003 is not tested for compatibility with Windows 10 so at any time an update can bork it (and there have been some complaints of this happening but a reinstall usually fixes it). I noticed back in the day that upgrades to Windows 10 as well as clean installs of 2003 in 10 sometimes had it automatically run in compatibility mode but it mostly worked. 2007 was always compatible from the earliest builds of Windows 10 but 2013 was recommended then.
Office 365 (next year's name Microsoft 365) defaults to storing your documents in the cloud (usually OneDrive) but you can change the default to your local computer. While you are editing the document though, backup copies are kept in the cloud "in case" you suddenly want to change to editing it on your phone or other device like an X-Box because that makes all kinds of sense when you have an actual PC. It's kind of a similar situation to Google Cloud Print which sent anything you printed (like your taxes) to Google servers where they promised not to use it for anything except to "improve printing" in that they claim the traffic sent both ways is fully encrypted so only they can read it. There are of course now a couple attempts at class-action suits against Google for surreptitiously collecting information anyway when in "Incognito" private browsing modes, and it seems Google (old slogans: "Don't be evil" and "Do the right thing" ) paid extra special attention to collect such data when such modes were selected.
"Office on the Web" (previously known as Office Web Apps) is a lightweight free version of Office 365 that runs in a web browser, and privacy concerns are such that organizations such as the Dutch government that allow the use of Office 365 disallow the use of Office on the Web. Apparently in the latter, Microsoft sends all of your embedded videos in your documents to 3rd party Giphy and personal telemetry data to Optimizely.