Rewrite is rarely the best approach. The best approach is to refactor it by order of importance. Break it up and go from there. If it's not broken, don't fix it.
The best approach is to:
-Assess the situation
-Create a task list
-Decide what needs immediate attention
-Create a time line for it all
-Get feedback from team
-Add the business roadmap to you list
-With upper management work on a timeline
-Define your project with realistic times
Execute and manage the project.
It took 12 years to get to this point so don't expect to change it overnight.
BTW, this type of team and codebase is not out of the ordinary. Companies start to program with the idea that eventually the problems will be fixed yet it never happens. Upper management does not care because all they care about is reducing cost and getting the results they need. You're dealing with the results.
The problem here is normalization of deviance across the entire organization. That has nothing to do with tasks.
The task #0 is sit down with the team and ask them to say in their own words what do they think about the project, about their engineering good practices, etc. See how aware are they about the problem they have created.
Try to understand how the status quo became normal and acceptable, before the same thing happens to you.
If this shit happened in the first place was because likely everyone was too busy living in their Jira alternate reality where you benefit from the perverse incentives made possible by the lack of visibility on code quality.
The best approach is to:
-Assess the situation
-Create a task list
-Decide what needs immediate attention
-Create a time line for it all
-Get feedback from team
-Add the business roadmap to you list
-With upper management work on a timeline
-Define your project with realistic times
Execute and manage the project.
It took 12 years to get to this point so don't expect to change it overnight.
BTW, this type of team and codebase is not out of the ordinary. Companies start to program with the idea that eventually the problems will be fixed yet it never happens. Upper management does not care because all they care about is reducing cost and getting the results they need. You're dealing with the results.