.browserslistrc, .babelrc, .editorconfig, .eslintrc, .prettierrc, .stylelintrc, jsconfig.json, package.json, src/index.html... and this is with a "zero config" Parcel setup. And that's not counting the src/vendor/ folder of two dozen files that only exist to work around old AngularJS libs expecting everything to happen in a global context and there still being no bundled that can handle those properly.
For example, agile vs waterfall (when there is no such thing as a "waterfall"; there is such a thing as cluelessness, though).
It's most readily observed in Web dev, where every five years or so the entire landscape is changing because a new generation can't be bothered to understand what came before (or, in fact, where the de facto mainstream stack has grown too many idiosyncrasies). For example, I'm expecting a back-to-basic-Ajax movement at the end of the React hype cycle, similar in spirit to motherfuckingwebsite.com.
Curtis Yarvin (urbit), Terry Davis (TempleOS), Alan Kay and Niklaus Wirth are people who don't follow the others.
Where I take offence to it is in how it's used in shitty consultancies, startups and agencies. If you're asking me to build a linked list in an interview where all I'll be doing is maintaining some shitty CRUD app in procedural PHP then it's a sure-fire sign that the company is a terrible place to work, and the people in charge have no business being there.
Similarly, feature/scope creep seems to be a big problem in this field too. It's not as common as projects taking too long/costing more than expected, but still pretty common none the less. Usually because someone didn't actually ask the customer what they needed before building it, or feel like telling someone that they can't just 'have extras thrown in for free midway through development'.
Documentation too. We desperately need more people to willing to write/update that stuff, especially where free software is concerned.
But even just between projects I feel like I lose a lot, rewriting things that I've done before, but slightly different. It's maddening.