Speaking from the systems side of things - it's plainly obvious when you get a piece of software where the developers don't understand the system level at all - it's obvious they only understand things at an abstract, programming level, and don't really understand how their software is going to work in the real world.
(The software will do what it's supposed to, and they may have implemented some fancy algorithms, but it will be a PITA to debug, PITA to install, PITA for every sysadmin who has to touch it, and PITA to try to design systems to support it.)
The point of doing the low-level projects is to learn for yourself, not to literally create the best new language (but you never know.)
Sure, like I said, if your goal is just idle curiosity and a desire to learn, that's fine. But it's kind of moving the goalposts to frame that as "creating a programming language" rather than "fruitlessly messing around with the science and techniques behind programming languages."
The point of doing the low-level projects is to learn for yourself, not to literally create the best new language (but you never know.)