Ask HN: Strategies to improve after finishing a product

Hello there, a colleague and I have just finished developing our first application for a client and we want to keep/improve upon our underlying technology. But now we are wondering, how do we know what part of the Framework(s) should be kept from the project, swapped out or removed? And what should be prioritized. What are your strategies for deciding how to proceed after wrapping up a project and can you recommend any resources on this topic?

Thank you in advance!