Ultimately you're in business to convince customers to pay you money in order to use the thing you built. If the code base goes to hell after making customer-r

Ultimately you're in business to convince customers to pay you money in order to use the thing you built. If the code base goes to hell after making customer-requested improvements to the MVP then that's a problem with the design of the MVP code base combined with a lack of refactoring to improve said design. It could be that management didn't want to spend the time or money to rebuild the codebase to let those new features be added in an organized way; that's a management problem. A very experienced developer/lead could translate from nerd to English and from English to Management so the people in charge could understand why they needed to not get new features for three months while the code gets refurbished. If management still says no, because there's no money or they've got impatient customers then that's a different issue.