How about enforcing direct control about Microsoft business? Not just another “low” fine in the ten to twenty billion range. Just stopping Microsoft, Apple, Google, Facebook and Amazon.
Enforcing AT&T to not enter any new business worked well. In consequence we got UNIX, C, open-source and documentation and finally the TCP/IP-stack of BSD, GNU and Linux. This had a positive effect for the complete computing industry and society. Reagan relaxed all rules, allowed AT&T to split up - the results were bad. No IT company had to fear any regulation afterwards, either politics didn’t want regulate or didn’t understand computing at all.
We don’t need this companies with too much power using incompatibility, vendor lock-in and storing away our data (the newest approach).
Chances for regulation Europe seem a little better? Less lobbyists and less tax money involved and people don’t believe in capitalism. Too late (10xtimes) and too little but at least they react.
EU cannot tell Microsoft in general what to do.
And after some (hard) years of actual competition benefits of compatibility will lead to lower prices and more choices.