ComfyUI supports 4o natively so you get the best of both worlds, there is so much that you can't do with 4o because there's a fundamental limit on the level of control you can have over image generation when your conditioning is just tokens in an autoregressive model. There's plenty of reason to use comfy even if 4o is part of your workflow.

As for LoRAs and fine tuning and open source in general; if you've ever been to civit.ai it should be immediately obvious why those things aren't going away.