Should startups still rely on 20+ different tools, or is it time for an AI Operating System?

No, never. Back in the early days of AI, you could have asked ChatGPT questions like how to write a Frida script to hook a certain function. It would have answered you with no questions asked, but the state is so bad now that even if you try to debug your own program dump, it will refuse directly. Back in the day, I could have thrown a sample 100 lines of code or a text file and asked it to edit it. It would have done that and given it to me with no questions asked, and now, no matter what prompt I give or how I frame the request, it doesn't do that. You see, the point here is that those independent systems are input and output machines. You provide input, and it will answer. Their capability won't degrade over time, it only improves. However their quality changes, those independent tools have years of LTS. You can choose your version of software and stick to it. Hell, you could rely on them. You can't rely on AI for anything. With AI being in total control, they could easily press a kill switch on you, saying you didn't follow the rules, blah, blah. My final thought on AI. Use it, use it every day. But use it only as if it were your servant. If you need it for things that are beyond your current capabilities, it would be better to learn those things first yourself.