Making an existing book app better - viable startup?

Hi team,

I'm completely new to the startup community and would love some advice.

There is a particular android app which I use to search for books, catalogue books and engage with a community of readers. However, it doesn't do it well.

A large portion of the reading community would seem to agree that the app needs a major refresh (based on google play reviews and other online forums). I would also love for the app's owners (a huge tech company) to incorporate all the feedback it has received however it hasn't noticeably done so for several years.

Would basing a startup on significantly improving an existing, highly downloaded, but poorly rated app be a viable business idea?

Keen to read your thoughts and advice.

Cheers!