[tdumitrescu]

Agreed with everyone else here that it's great that you've recognized areas of improvement for yourself. That's an important step, and in your position I would validate by chatting with your coworkers about it. Every time a colleague has asked me for my opinion on what they can improve upon or work on, I've always tried to give a straightforward critique; see if your colleagues independently bring up the same issues you think you have.

More generally, without having worked at a company that size yet, you can't be expected to come in with all the domain knowledge that dev team veterans have. Forget about titles like "senior" and what that means. Doing mostly-solo dev work for a long time is just a very different kind of work than writing code in a shared codebase with a team of coworkers of varying experience and skill levels. There will be aspects of maintainability and clarity which simply aren't a big concern in your solo projects but make a big difference when you have dozens or more developers working on the same code. Communication with coworkers becomes an important skill, collaborative project management etc. These are things which you can't just study and learn on your own, you ramp up on them over the course of working in that kind of environment. So yes, you might be pretty "junior" at some of these medium-sized-company aspects of software development, but that's fine and only to be expected at this stage. Keep at it, gain experience, level up by doing.