The problem with bespoke, homegrown, and DIY isn't that the solutions are bad. Often, they are quite good—excellent, even, within their particular contexts and constraints. And because they're tailored and limited to your context, they can even be quite a bit simpler.
The problem is that they're custom and homegrown. Your organization alone invests in them, trains new staff in them, is responsible for debugging and fixing when they break, has to re-invest when they no longer do all the things you want. DIY frameworks ultimately end up as byzantine and labyrinthine as Kubernetes itself. The virtue of industry platforms like Kubernetes is, however complex and only half-baked they start, over time the entire industry trains on them, invests in them, refines and improves them. They benefit from a long-term economic virtuous cycle that DIY rarely if ever can. Even the longest, strongest, best-funded holdouts for bespoke languages, OSs, and frameworks—aerospace, finance, miltech—have largely come 'round to COTS first and foremost.
The problem is that they're custom and homegrown. Your organization alone invests in them, trains new staff in them, is responsible for debugging and fixing when they break, has to re-invest when they no longer do all the things you want. DIY frameworks ultimately end up as byzantine and labyrinthine as Kubernetes itself. The virtue of industry platforms like Kubernetes is, however complex and only half-baked they start, over time the entire industry trains on them, invests in them, refines and improves them. They benefit from a long-term economic virtuous cycle that DIY rarely if ever can. Even the longest, strongest, best-funded holdouts for bespoke languages, OSs, and frameworks—aerospace, finance, miltech—have largely come 'round to COTS first and foremost.