Rejection is an inevitable part of the job interview process, but it doesn't have to be the end of your journey. Take each rejection as a learning opportunity and come out stronger than before.
Your job isn't to turn user stories into code. The company has a mission. Everyone at the company is hired to push that mission forward. You're not a software engineer hired to code. You're a human hired to push their mission forward. It just so happens that you are a human with coding skills and during the hiring process, they recognized that those coding skills could help them in their mission.
You may not have enough information to perform the analysis. You may need to ask the product manager questions about the features and how they tie into the mission of the company. Go into the conversation with an open mind and a desire to understand. The company hired the product manager to help prioritize work in the optimal way to push the mission forward. You should trust them to do their job well and recognize that they may have context that you're missing. So long as you effectively expressed all the information you can about the long-term benefit-to-effort ratio of your ideas then you've done all you can there.
If you join a company or team and deal with constant nonsense and a broken culture? Switch. Immediately. Do not delay. And if the new team is nonsense again? Switch again. Don't let these people waste your time or tax your peace.
You will do your best work when you are supported and included. You will make up more career time working 6 months at the right place, than in the previous 6 years of daily hell.
An inclusive team will not judge you for switching multiple times finding the right fit. And hiring managers, have more confidence in your ability to create an environment that people want to stay at. The past at other teams and other situations doesn’t predict the future at your team and this situation. I have seen so many “jumpy” people find their “home” after so many jumps. Sometimes it’s the first decent manager they have, sometimes the first company they can grow with and so on...
Don't ask people why they left their last position. They often can't tell you, and it's not relevant. Instead, ask what they are looking for in their next role. You can even ask how long they intend to stay, or what would entice them to spend N years on the same team or role.
The divide between frontend and backend engineers is increasingly less useful:
Product Engineers consider the frontend, backend, design, and everything in between to create a great user experience. They don't need to understand every part deeply, a common misconception of "fullstack". Instead, they have a broad understanding of the available tools and deep experience applying those tools to build products. At Vercel, we updated our job descriptions to change references from Fullstack to Product Engineers.
While Product Engineers focus on building and enhancing features that solve end user problems, Platform Engineers focus on the infrastructure that supports the product.