I suppose so. I like to think my custom plugins are well written and maintainable. I attribute this to the fact that I identity as a JavaScript engineer with some classic OO tendencies (shout out to Gilfoyle). More or less I write JavaScript and Java/C# so I'm not some dipshit writing WordPress plugins w PHP/Wordpress as my first and only language and framework.

The nicest plugin I've seen [code wise] is the Jasig CAS authentication plugin, and for that I had to modify it to specify the behavior I wanted (custom 500, 501 screens, don't upsert user). So, whenever an update comes around I have to either ignore it or modify the code. Honestly, I think that's even against the license since I didn't publish my changes.