So the thing is whenever I export, my videos have less colour and less detail than the way it looks on the Composition preview on After Effects. Why is that and what can I do to fix that. I know everything about the right export settings, I have tried a variety of things from increasing the bitrate to upscaling the video to 4k. What should I do?
Compressed video will always look less sharp than inside AE even at 4k. There's no way around that. The rest are probably color management issues (and lack of CM), compounded again by the limitations of how compressed video handles some colors. Anyway, without exact info, screenshots and so on this is kind of a pointless discussion. For all we know you could simply work on an overcranked 32bpc project and then be disappointed that things don't look HDR-ish anymore when converted to MP4. So for what it's worth, you have to be much, much more specific and provide the necessary details.