They've already tried to kill it like a year or two ago with their last major API changes. This is just another attempt at it.

Google may be wealthy, they may be in control. However, they're still limited by how the technology fundamentally works. You can only secure something so much before you inadvertently damage your own product's functionality by restricting its access too aggressively.

Another thing to remember, YouTube is used by literal billions of people across the entire planet from virtually every notable OS capable of doing so. Locking it down so that only one type of app and web browser can access it would cause them to lose millions of eyeballs and ears, i.e. hundreds of millions of dollars in revenue over time. It'd have the exact opposite effect of what they're trying to do (increase ad profits).