The difference between a senior engineer and a junior engineer to me is that a senior engineer knows how to evolve a system into the system that they want/need it to be. They don't just say "well, looks like we have to throw the whole thing out the window and use this other new shiny/rebuild it from scratch". The desire to reinvent is important to keep throughout your years as long as it is rooted in reason and in the best intentions of the team and company.
Riffing on that, more senior engineers better know how to evolve those systems (whether that is working with larger systems or working on people problems or working to support large customers, etc)
Whenever I've "started over", I've sometimes longed for going back to pre-existing stuff and evolving it. Sometimes, but not always. Whenever I've 'evolved' existing systems, I've almost always wish we'd started over (or some variation thereof).
Recent-ish project: holding on to multi-year old legacy data that was simply bad/broken (but was assumed to be good because it was barely used/examined), then requiring every single new feature to work flawlessly with broken data, ensuring that legacy customers 'never' hit an error (when 95% of them have not logged in in years). That's a candidate for 'rewrite from ground up' - you can keep an old system going in maintenance mode, build the archetypal "version 2", then decide if/when/how to migrate old data over...
Knowing that you can 'evolve' a system towards improvements and knowing when you should do that is another sign. Something may be technically possible, but the time/effort/cost can outweigh whatever benefits there may be.
Riffing on that, more senior engineers better know how to evolve those systems (whether that is working with larger systems or working on people problems or working to support large customers, etc)