If you are interested by rendering stuff with EEVEE, you absolutely don’t care about CUDA.
And now, with OIDN, you can render with Cycles in CPU mode without giving a shit to GPU rendering.
Cycles who has a GPU rendering initially designed on CUDA, is providing a way to do it with OpenCL.
Situation could be different. There could be none.
External renderers are allowed. You can render a Blender scene with LuxCoreRender or AMD Pro Render.
In fact, situation never was as good to do fast rendering on a large variety of hardware.
So, no, last powerful and costly NVIDIA RTX card is not an obligation to work with Blender.
And if you are only making 3D Printing from Blender’s sculpts, rigging characters, doing VR stuff, 2D animation. You can live without caring about rendering at all.
There will always be a large diversity of Blender users with different hardware set-ups because there are a large variety of Blender uses.