i would say that it is big tech just because windows
but a lot of developers don't include it, it's not part of the big 5 of FAANG which is where everyone wants to work
i haven't used a microsoft dev tool or platform since like 2005
They're one of the largest tech companies, with them, Apple, and Amazon tending to trade the top spot for valuation.
That's not because Microsoft is not big, in fact its typically for the total opposite reason that Microsoft was too big so they shunned them. Meh, if people are clamoring to work for Facebook that doesn't tell me anything with regards to it being a big tech company. Facebook is half of what any of these others other than Netflix is worth and seems to be often close to shooting themselves in the foot and killing their already too ballooned valuation.
You actually probably have. Microsoft has been doing quite a lot of open source development in the past 10 years. Hell I think Windows now might even include a full blown Linux distro embedded within it because of how useful it is for developers.
The new Windows Subsystem for Linux will use a real Linux kernel.
arstechnica.com
Your knowledge of things seems to be stuck in 2005 and even then is skewed in some bizarre fashion.
Also if you search for FAANG (now FAANA) even Google goes out its way to include Microsoft by going "you mean, BIG tech right?"