Like I say everytime these posts come up, at least as it relates to the Engineering side of things. Engineering in particular isn't about how smart you are. You can't be brain dead of course but there are plenty of "Smart" people who go into engineering and flunk out or quit. Its more about perseverance. Almost like a hazing ritual to be honest. I wasn't the best in math for example growing up and I can't recite a billion prime numbers off the top of my head now either. However, as long as you're willing to put in the work, I would say most people who are at average or above average intelligence can do the work and learn the material. You just need to have the drive to do it.
To tie into what I said above, its mostly laziness. I've seen freshman go into the program and brag to everyone they know "I'm in engineering" "I'm an engineer ( while in school still

)" and all this other shyt to make themselves seem like big shyt, yet they're gone after year one or two. Just a personal anecdote, I had a dude In my group during a physics class who did this shyt on his facebook page all the time. Yet he only showed up for like 3 - 4 recitations during the whole semester. I didn't see him in the second year section of the physics series course either

.