It was a whole new kernel. They didn't rewrite every single utility, but the kernel was a rewrite along with things like diskpart and the boot loader. The core of the OS. They also dumped all of the old 16 bit legacy apps.
And then starting with Vista, Windows went to 64 bit. It was a complete rewrite of Windows and is way more stable because it requires every driver to be signed by Microsoft. You can disable the signed driver requirement, but then you're risking stability.
This might come as a shock to you, but Windows 95 isn't even an operating system. It's a GUI shell that runs on DOS, which is a 16 bit operating system. There is no Windows 95 kernel.
One of those really sleazy rooms with the heart shaped jacuzzi that has the DNA of thousands of people clogging the pump. And a bed that vibrates if you put a quarter in it. And wood panel walls.
To be fair, it's more selfishness than malice.