If you have a sub 3.0 GPA, yes med school is out of the question. It’s recommended you stay above 3.5-3.6 for best chances (which are about 1 in 2).
The dynamics of med school “not working out” is that once you get to some college classes, working hard is a necessary prerequisite but not sufficient; you may work long and hard and very seriously at organic chemistry or biochemistry and just not make it. In many first year biology classes (and even more so in engineering), the average is in the 50s, sometimes in the 40s. Remember that most of the kids in these classes were good students in high school. There may be some outliers but they’ll drop quickly. Everybody else in that class had good science grades in high school. And the average will still be very low. That’s the concept of “weed out”: the exams are designed to make students fail. If you can’t be in the top of your first-year classes, odds that you’ll pass organic chemistry are nil. Fortunately students take a lot of different classes so they can choose the best major for them.
In addition, you can’t juste “retake” the MCAT until you get the proper score. You can take it exactly twice, and the threshold for a second-time taker is higher than for first time, so essentially you have to get it right, right away. The test has three parts over 2 days.
You can read more about it here:
https://www.aamc.org/students/applying/mcat/about/422306/changing-the-mcat-exam.html
Even if you do everything right, it’s not a slam dunk. You have the interview, which will be based on your research/clinical experience (shadowing, volunteering, etc) and you have to train for that, too.
The reason people say premed engineering is not for the fainthearted is that med school admission depends on a high GPA, whereas engineering suffers from notorious grade deflation (ie., a 3.0 is a good engineering GPA… but not for med school) so you have to be very sure of yourself when you choose an engineering branch along with premed. You can also ask around when you choose your engineering specialty for one that isn’t the hardest - it’s still engineering, but it won’t be a herculean task to get to med school. Chemical engineering is rumored to be the hardest, but check with your university.
Yes, engineers followother people’s ideas - researchers. These researchers may have started out as engineers, worked a bit, and went back to school for a more advanced degree; with a master’s degree in engineering you move to management, with a PHD you are in research/development. Engineers often work in teams and those teams, together, put the researcher’s ideas to life, but they have to use their ideas too.
Physicians will never be replaced by robots 
and this is reflected in the new MCAT and new premed core courses: the human factor is essential, which is why people say medicine is both a science and an art. You won’t be a lab technician, a medical examiner… you’ll work with living people who may not know themselves, may have ailments they don’t know how to describe, or can describe very well but in another language, have a different belief system than yours, will be drunk or dangerous or smelly, will be small and cry a lot, etc, etc.