Creating animations is one of the MOST time intensive development tasks. Even crap quality animations will take time to render. Let's say it takes in average 2 minutes to render one frame, a 5 seconds animation at 30 fps will need 2 * 5 * 30 = 300 minutes (5 hours) to render.
That is, if the rendering process doesn't crash in the middle, and you don't discover an artifact or oddity that requires you to redo some or all the frames (or that you find out that the scene doesn't work and you have to scrap all the work, and start from scratch)
If you think that is not that bad, I'm ignoring designing, composing, rigging, finding the right assets, creating assets, post work and audio (and I'm still skipping other required tasks)
Increase complexity (reflective surfaces, complex materials, the number of assets and light sources), image resolution or frame rate, throw in a few effects and your render time will at least double or triple itself (or even more)
And no, having a 3090 is not a magic bullet.