Centralized only became mainstream when everything started to be offered "for free". When it was buy or pay recurrently more often the choice was to buy.
There are FOSS alternatives for about everything for hobbyist and consumer use.
Making software that is polished and reliable and automatic enough that non computer people can use it is a lot harder than just making software. I’d say it’s usually many times harder.
If computers came with Debian, Firefox and Libre Office preinstalled instead of only W11, Edge and with some Office 365 trail, the relative difficulty would be gone I think.
Same thing with most IT departments only dealing with Windows in professional settings. If you even are allowed to use something different you are on your own.