Does it make sense to sell backend / fullstack libraries?

Question

Backend

Good afternoon friends!

Goal:
Sell complex backend/fullstack libraries. I'm not chasing big money, I want to do what I love)
You, software engineers, are my potential clients.
Questions:

1. Does it make sense?
   
2. What else (not) needed in product specifications?
   
3. backend or full stack?
   
4. What's better? In particular, any parts or whole flexible features, with REST / GraphQL Api?
   

Who am I:

1. Front end engineer;
   
2. Worked on incomplete Scrum / Agile, but read about and ready to apply Extreme programming and Agile;
   
3. I know Software design, TDD, BDD;
   
4. DDD theory, applied its principles when learning requirements;
   
5. I will pass https://portswigger.net/web-security and https://web.dev/secure/ ;
   
6. I will be a UI designer;
   
7. I will be a backend engineer
   

Who I am not:

1. Did not work as a security specialist;
   
2. Did not participate in open-source;
   
3. Not a DevOps engineer;
   
4. I don't speak System Design (Large scalable distibuted systems:
   Web Scalability for Startup Engineers - https://amzn.to/39c55QV ;
   Designing Data Intensive Applications - https://amzn.to/3fxgOLm ;
   Building Microservices - https://amzn. to/2UUPsFi ;
   System Design Interview - https://amzn.to/33gpRev );
   Did not work in large companies (Yandex, Google, Amazon, ...)
   

Product Features:

1. High-quality GIT log;
   
2. Documentation on https://diataxis.fr/ eg https://www.gatsbyjs.com/docs/quick-start/ ;
   
3. Security, by one's own efforts;
   
4. Semantic versioning;
   
5. High-quality, thoroughly tested code;
   
6. continuous delivery
   

Answer 1

1. back is a very vague concept.
2. backing is very tied to the language and wishes of a particular person.
I would not bother with the back at all and only do the front.