A 5-year old thread receiving some necroposting...
Oh well.
It does take time and effort. Even Linux started out simple - because it was an incredibly smart guy at University of Helsinki doing it (yep, same guy who invented Git!)
An OS is a plenty complicated puzzle. Code versions for different components have to match. And that list of components is pretty long, too. And you gotta make sure all the components play well with each other. And you gotta have hardware that is powerful enough to compile stuff over and over again.
You also have to have to be able to set up shop correctly, and line up the toolchain so that you can just pop out an ISO that you can install. It's an endless rabbit hole. You gotta be able to reconsider your decisions every step of the way.
And then that toolchain requires maintenance, too. Vast majority of people who try to roll their own Linux distro or a BSD version - even if they succeed in putting something together from up-to-date components at some point, and it somehow works OK at that point in time, there's still a ton of maintenance needed. No one-dev show has been able to keep up with the required maintenance for more than a year or two. And that maintenance includes security-related patches, bugfixes, and whatnot. For an OS to work awesome, you can't be "Jack of all trades, master of none".
There was a famous example of someone who actually tried to pull it off - the TempleOS guy. He actually had something going for a few years, it worked much better than what can be expected from a one-dev show, but it didn't last.
With that said, it can be a fun hobby to try and pull together something on your own hardware - just keep in mind, the Internet is already littered with abandoned projects like that. I would not want to use a disposable OS that somebody slopped together without much consideration for QA. Harsh words, but that is reality. Even on a toy device, I'd rather have decent quality firmware that I can rely on.
I remember really liking CyanogenMod. When I discovered it, it was aready a well-developed OS, well-supported on many devices, and the toolchain was obviously well-organized. These days, it's called LineageOS, and it's a
fork of Cyanogen - someone liked Cyanogen enough to put in the effort it takes to continue the project. Many have tried to replicate the success of Cyanogen/Lineage, but the best anyone could hope for is a model-specific phone ROM of dubious quality. I'd know, I tried them. And even then, most of those ROMS are for older phones that are no longer on the market, and the projects are effectively abandoned. Even if you can download a ROM and find instructions on how to install it, you'd usually see comments indicating that the ROM is no longer in development.
Even big and popular Open Source projects have a difficult time sustaining themselves. Apache Foundation's Subversion is being edged out by Git, Xorg is running out of money to host their own development infrastructure, and there's more stories like that.
There's lots more reasons and examples why developing an OS ain't easy. I consider myself lucky that I was able to find out about FreeBSD and make good use of it. Yeah, it's largely a DIY, and it has its drawbacks, but I can live with that, because the benefits I derive make it worthwhile for me.
So, no, it's not "all of a sudden". OS development faced very different challenges in 1970s and 1980s than in 2010s. Lack of access to tools and infrastructure was an issue in 1970s and 80s. Also, back then, there was not a lot of material to learn from.
mrmtsenga , you might benefit from watching a few documentaries about what UNIX development was like back then. With the Open Source movement (which was created because one MIT dev got pissed at a colleague), the challenges of OS development are pretty different than in '70s/80s, but they are challenges nonetheless.
