As someone who has just had the chance to be promoted to Senior I can say this is very much on point 🙂. Especially the social/soft skills part.
I think the problem with being quiet and not communicating enough, is that it might make other people think that you're uninterested (while you might be very much interested in everything that's being discussed). This might lead to people involving you less in brainstorming sessions or other discussions, which gives you less chances to show your skills and desire to contribute to the project.
I think this mostly happens because people think that if they speak, they'll say something stupid or too obvious. I don't think stupid questions exist, and if you feel too reluctant to ask something, you can just start by stating an opinion about something, maybe you like the idea for a new feature, or the new project seems exciting, you can start with simple things, when people notice you more, they'll be more prompted to ask about your opinion as well and that is a great way to boost you confidence.
Keeping track of your progress and success is very much on point as well, it really helped me become more confident and it's really going to be the proof of why you're ready for the next step on your career.
That's how it has mainly been for me, there can be other factors as well but I think this post includes all the essentials and I wish I could've read something like this a few months before😄.
Thanks a lot Katy!