50/50 It's what employers look for in Senior Engineers, but junior engineers are often hired on pure tech. Historically there was a high amount of BS where people would take credit for deliveries that they were only tangentially a part of, or get ridiculously lucky on their first big project.
It's next to impossible to hold an engineering team together to even KTLO if you don't have some project which grow's their careers.
The number one requirement for Senior Engineers is their extensive experience with the company's tech stack. At least that is what is written in job ads outside of FAANG. You're probably not passing the HR stage when you have experience in Java but the company is looking for a senior .NET developer.
It's next to impossible to hold an engineering team together to even KTLO if you don't have some project which grow's their careers.