Exported video looks different to timeline monitor

Exported video looks different to timeline monitor - The exported video looks brighter and not as saturated compared to the timeline monitor which is exactly how I want the exported video to look. Why is not possible to match the exported clips to the timeline. Please someone help me I've been researching this for months and still cannot get a clear and defined answer as to why this is such a huge problem. I'm using a Mac by the way, Thank you

There are hundreds of posts about this issue. Search these forums.
If the rendered file matches the viewer when you re-import it into Resolve, then it's ok. Different display software will display differently! Quicktime & Resolve will look different on playback.
This is just ONE of the reasons it is common to have a calibrated monitor fed from a BMD Decklink or other BMD display device.

Now I have to take another drink! Read these:

"Grading for Mixed Delivery: Cinema, Home, and Every Screen in Between" by Cullen Kelly
https://blog.frame.io/2019/10/14/gradin ... -delivery/

and

"How to Deal with Levels: Full vs. Video"
by Dan Swierenga
https://www.thepostprocess.com/2019/09/ ... l-vs-video

and I think both cover the issues and the solutions very well. These videos also cover it:

Understanding color management is also helpful:

"Color Management for Video Editors"
https://jonnyelwyn.co.uk/film-and-video ... o-editors/

The above articles will explain why things change on different displays, different playback engines, and the importance of calibration and color-managed outputs.

I generally try to export a second or two of SMPTE Bars at the head of the project, and I import the file back into Resolve to check it on scopes to verify all the levels are correct. Using calibrated displays is a must -- without that, you have no idea what you're looking at. We also accept that the basic picture is always going to change a little bit on different devices, different OS's, and different browsers, because that's life.