I started working at this company about a year ago. I work on a team that maintains their web application.
The web application was built about 20 years ago using Java Spring and is extremely outdated with a fair amount of not-so-great code. It even uses XSLT which I think has been outdated since the early 2000s.
I feel like we are on an old wooden boat that has plenty of holes in it and we just keep putting duct-tape over every new hole as it comes up.
To me it's obvious what needs to be done. We need to completely make a new system from the ground up using updated web technology. It is a complicated system that would take time but I think it would be 100% worth it. My idea would be to pay whatever you need to to hire a senior web developer to maybe spend a year or so (or however long it takes) creating the new system. However, I am not in the position to make this call.
So I've come up with the idea of developing a simpler version of the web application (using React and FastAPI) in my free time. It might take me a few months. Then when I am ready to show it off, I can show one of my managers and see what they think. This would help to prove the point that if a somewhat junior developer can do this in a few months, then maybe a team of senior developers can do it in a year. It would also help show the potential of how nice and easy the new system could be.
I'm just worried my managers might feel like I am overstepping and that I am insulting their system (note that one of my coworkers on my team is one of the ones who built the system roughly 20 years ago). What do you guys think?