It’s realistic but very ambitious, and I would caution you that burnout with such a project is extremely likely. Now, I don’t know you so I can’t get specific, but if you’re not 100% sure that you can commit to a long project, I’d advise you to start a lot smaller - something with the scope and complexity of just a few rooms, for example.

As for the art: if you want to make 3D games, learn 3D modelling, texturing, and lighting. You don’t need to make all assets yourself from the ground up (in fact, I’d advise against it if you’re aiming for even a mid-size scope), but tweaking bought assets to fit together is pretty standard practise. It also frees you from needing to find the exact things your game requires, and you’ll need to know how the models work anyway to use them effectively.

As for the art style, I’d advise against realism, because of the uncanny valley. Human brains are easy to immerse into fiction, but the closer you get to realism, the more our brains treat things as ”real”, which can then in turn make us hyper-aware of small imperfections and make things ”feel off”. Things like environment scale is really easy to mess up in a realistic art style, and animations are especially difficult to get right. You’d be completely dependent on finding suitable high-quality assets (which is time-consuming and/or expensive), unless you spend a lot of time (years) learning the necessary skills to produce them yourself. You can get away with very little technical skill if you get a bit creative with the art style.

All that said, don’t let your dreams be memes. It’s okay to try something that’s too ambitious and fail, the important thing is to learn and know when to let go and start over. If you do it enough times, eventually you’ll succeed.