JLPT N2 Grammar - だらけ

The video tutorial is presented by a liberal arts student of JLPT N-tsu, focusing on expressions used to describe abundance. The lesson includes examples such as a room full of garbage and a test full of mistakes, illustrating how to convey the idea of 'many' or 'full of' in different contexts. The tutorial concludes with a final example involving a ramen shop full of salarymen.

What does the speaker mean by 'I should have studied more'?

Describe the situation in the ramen shop as mentioned in the text.