That's a great topic and article where I could rant about all-day long :D
My main issue with most juniors is their cockiness, ignorance taking advice from more experienced colleagues, arguing about things they don't even know and understand, and ending up doing something completely wrong.
I've been doing Full-Stack development for about 20 years and earn money with my hobby for nearly 17 years. For the past ten years, I've been mentoring juniors every year, and it becomes more and more difficult finding the right people where you invest time into. Within the ten years, only two out of ten juniors turned out well-doing developers and the others we had to let go as we didn't see any improvements after more than a year of trying.
Juniors often forget to take their work seriously as companies tend to play down or ignore mistakes, even though those mistakes were terrible for the business. They also forget that the time we seniors spend on them to help out, review work, or explain things, etc. is extra work and goes on top of our work. Same goes for deadlines they miss or sprints and tasks they couldn't finish and didn't inform us till it's too late.
Sixteen years ago and in my first junior year, I've learned my lesson, where I had to build an online advent calendar script for our customers with prices every day, and I fucked it up. I was so cocky and convinced my colleagues that my script works, so we put the calendar script online without code review or test. The calendar then exposed on day one all other days, caused by a faulty conditional check in my logic. Even though the seniors at the time were responsible for reviewing my work first, it was my arrogance and cockiness that brought me to this point, and it hit me hard, let me tell you that! After this happened, I was more focused on my work; I did listen more to experienced devs and gained the ability to learn from my mistakes.