"every book I've read, every professor I've talked to, every lecture I've attended" pretty much says it all.
Some of us have been in this game a long time. Decades. Some of us still love the subject and, unlike the more recent crop of 'developers' still care about efficiency and choosing the right tool for the job. Smaller, more efficient, low power consuming and easy to program 8/16 bit units are used all the time, and for good reason. An RTOS does add additional overheads and can consume precious clock cycles and, thus, current. Sometimes that trade off is worthwhile but, increasingly in the world of IoT, the relevance of these 'ancient' ideas are again being seen as critically relevant.
Given your comment, I can only assume you are still in school or have only just left it. That means that, no matter how good your academic record is, and no matter how clever you think you have been with any little amateur/school projects you might have completed , you are still wet behind the ears and, apparently, quite arrogant. Give it a couple of years before shooting your mouth off as, while not all, quite a few of your elders are your betters.
PS. Good move on posting as an AC. It might have saved you a few lost job interviews.