I guess it depends on what people define it as. But I've seen many devs build custom harnesses of sorts, and spend lots of time on that to wire it all together, to then really not achieve much with them. Examples being tools or stuff that got superseded once mcps became a thing. Or spend hours making gigantic folder of skills that specified loads of stuff that the next generation model just could infer. Or build a gigantic parallel agent suite when the bottleneck wasn't the agents in the first place.