I agree that OOP is limiting, but Functional is not the fix. Table-Oriented-Programming is the future. Your code snippets for validation etc. could be associated how your domain prefers, and you can query them to be together by field or by any other grouping as needed. You just have to make sure you have the proper meta-data in place, such as field name/ID, entity, screen, event type, etc.

File-centric code forces a hierarchical big picture structure, but many relationships are either not hierarchical, or need additional non-hierarchical ways to view/group them. Relational is more powerful and more flexible than file systems. (It has some rough areas, but they can be worked around or fixed.)

Start backward next time and think how you would LIKE your code organized, forgetting about frameworks you know. If you do this often enough, you'll realize RDBMS-based code management is where we should be heading. About 90% of validation and field management could also be attribute-driven: data-dictionaries would do most of the grunt work.

With OOP and FP you are forced into choices such as "should this be its own class, or an object instance, or a group of classes for composition?" etc. etc. When tablizing your event & validation snippets, you are not forced to choose. They are grouped "by" anything you want, and by multiple groupings at the same time: multiverse. I agree that FP is probably more flexible than OOP, but it's also less disciplined: large FP systems look like the spaghetti-pointer databases that preceded RDBMS. Hierarchical, logical, and pointer-based DB's thrived for a while, but relational won, for a reason.