Should I be comfortable with back-end while applying for front-end jobs?

I've been interested in designing web apps and even coded some static pages when I was a kid, like 20 years ago. Life happened, and I took a different path. However, I've been still aspiring to have a job like a front-end developer.

I'm about a finish a full-stack web development bootcamp in Udemy by Colt Steele. I guess it's a little early for me to apply for junior level positions or even internships before completing my portfolio.

I'm wondering if a junior to mid-level front-end developer can handle the following:

Imagine a web application where users can view products and rate them and has the following features: Authentication, Product Listings, Product Details, Reviews and Ratings, and Photo Upload.

I think the most modern stack for this project is MERN. So I need MongoDB, ExpressJS, React and NodeJS for this project. For a project like this, you'd probably need a front-end developer, a back-end developer, and even a UI/UX designer. This goes beyond what I've been taught in the full-stack project at my bootcamp.

I understood the logic in the backend but struggled with it while watching. Shouldn't a front-end developer be at least somewhat comfortable in the backend for a project like this?

I don't want my portfolio projects to be limited to just landing pages or to-do list apps. However, tackling something like this seems to require a grasp of Node.js, Express, MongoDB, and even Mongoose, among other things. It's a bit intimidating.

What do you think? Would you recommend focusing on improving my JavaScript fundamentals and React skills while having a basic understanding of backend concepts, or should I work on thoroughly understanding backend logic before looking for my first job, even if it makes me more comfortable?