Claude Code CLI is just a software package, if Anthropic API is down you could always connect Deepseek/other provider API to Claude Code CLI...

The point is that, with a sufficiently complex setup (with skills, MCPs, prompts, etc.) the difference in AI models will impact the quality of work. You might not care now, but you might care when you have 2 million lines of code and zero idea whats going on.

The point is vendor lock-in. The vibe coding community has reinvented vendor lock-in and is bound to repeat every mistake associated with it.

Can you give an example of a skill or prompt that would work in Claude and not in the others?

Pretty much every single detailed prompt made after trial, error, and refinement is tailored to a specific LLM. They will all perform worse used with other LLMs than a similar prompt tailored for the second LLM would perform, and at times quite poorly.