That moment when you lose even more faith in humanity
Fortunately, there are still Linux distros that don't use systemd. Unfortunately, in the enterprise and server space (with good paid support), there is no way around RHEL (and SUSE to a lesser extent).
But Linux is (or was?) mostly targeted at sysadmins to begin with
Initially, it wasn't targeted at anything. It was a bunch of college students that wanted to play with computers, and the i386 made serious Unix-like playing possible. Since the 80s, we had all been dreaming of bringing up full 32-bit machines with virtual memory and demand paging, but the problem was that one couldn't get an unencumbered source tree. Minix sort of fixed that, but it was way too small, a toy system intended for academic instruction, not use.
At that time (late 80s, early 90s), the i386 for the first time brought inexpensive compute power with sufficient memory addressing to the masses. Before that, running serious software was expensive, because it needed expensive hardware (mainframes, VAXes, Sun, HP and IBM RISC machines), and the 68K and 32x32 based systems never became mainstream and affordable (with the exception of the Mac, but that was a closed system). Through the magic combination of DOS/Windows and Intel/AMD, in the early 90s there was suddenly compute power at a price point that really opened it to lots more people and applications: You could get a 32-bit machine with a MMU, multiple MB of memory, and a video card that enabled a GUI, for about $1000 to $2000. That caused a giant vacuum of inexpensive operating systems that could get serious work done on x86 machines, without the hassle and cost of licensing and having to pay support (both for hobbyists, and for commercial low-end use).
Linux filled that void. In those days, Linus was a fun and approachable person (I remember going to drink beer with him at "99 bottles of beer" in Santa Cruz a few times, long before he was married or moved to the US permanently), and a large army of people quickly built the infrastructure around his kernel that was necessary to build production systems (making distributions, setting up FTP servers, porting software, getting XWindows to work, and moving useful software to it). I remember the days when we first ported Fortran codes to it (initially using f2c), and ran X-based data analysis tools such as PAW, on a machine that cost less than a car.
The competition was on the commercial end system 5, but getting a license for it was punishingly difficult and expensive. In the BSD space, there was BSDI (which wasn't free, but very affordable, and the people who handled support contracts were friendly, unlike the SysV vendors). Then Bill and Lynn Jolitz completed 386BSD without using the AT&T encumbered pieces; but that was "too little too late", held back by a variety of factors: Linux was already succeeding, the Jolitz'es were famously obnoxious, the BSD core team was still in the Berkeley ivory tower (and not interested in x86 ports and at war with the Jolitz'es), and there were various lawsuits that kept all *BSD operating systems were under a legal cloud. In my view, *BSD didn't became a viable "competitor" until the early 2000s, by which point Linux had won the free operating system war (saying "competitor" is funny, given that until the rise of the RedHat business model neither made money, and that they actually more complement each other than compete).
But what is definitely true is that Linux, as usually distributed today, has gone down the path Windows blazed in the 90s and 2000s with NT: It's very complex, it's very black box, hard to manage and understand. The only difference is that you can run it without paying anyone; although in practice, if you want to use it in (commercial) production, you will need a support contract unless you are a superhero, because it is too complex to just work. From this viewpoint, systemd is exactly what the commercial Linux support ecosystem needs: it makes it more bizarre and complex, meaning that paid support becomes even more important. Note that Poettering's employer is also the largest vendor of Linux support.
