The main competition for Autodesk's Fusion 360 is SolidWorks. It's possible, although not that easy, to get models back and forth.[1]
There's FreeCAD. There are many low end 2D CAD programs. If you're building something bigger than a house or more complicated than a keyboard, though, you probably want a pro product.
[1] https://www.buildercentral.com/solidworks-vs-fusion-360/
Constructive solid geometry is hard, but it's all math. User interfaces for 3D CAD are very hard. Open source is terrible at hard user interfaces. Hence, no really good free 3D CAD.
Office + Windows + Active Directory + Windows Server is the only viable enterprise-level software stack for white collar office work. There is no real competition in this space and, as a monopoly, Microsoft charges accordingly.
Microsoft's monopoly pricing is passed down to every business' customers and, ultimately, extracts money from all of our pockets.
In my books, post the antitrust case against it in 95, Microsoft has been the least monopolistic of the bunch, and a net positive to the rest of the world.
All of the companies you mention have near-monopolies in their respective sectors. Hundreds of years of economic history show that monopolies are extremely harmful to their customers.
Autodesk is only able to get away with what it does because regulators allowed it to buy out its competitors. Further, the extreme technical difficulty of reverse-engineering complex file formats--including legal obstacles such as enforceable shrink-wrap contracts against reverse engineering, the DMCA ban on reverse engineering, and patent issues--means that it's virtually impossible for competing, interoperable, products to emerge in Autodesk's markets.
Microsoft continues to be a problem because the US government decided, 25 years ago, that stopping Microsoft from abusing its operating system monopoly was unAmerican.
Companies, like people, follow incentives. The incentives created by strong copyright and patent law, combined with the deliberate unenforcement of anti-trust laws in the United States, prevent competition. Without competition, customers always lose.
Getting users a fair deal means changing the rules that define the software market to consider the needs of users rather than only the wants of vendors.