Dark Mode on Mac OS Mojave not working properly on Macbook pro 15 2017

FWIW, I am just about to end testing with iStatmenus with Mojave and it doesn't seem to interfere with Mojave at all. I don't think that's what caused your problem. I think it was suggested you remove it just in case.

I do not use any third-party monitoring tools, so would not be able to offer any recommendation. Good that you have arrived at a functional Mac now with dark mode. I would recommend staying far away from so-called cleaner tools.

If you are running any anti-virus, fully de-install per vendors instructions. Reboot, and try Dark Mode again.

If the above is not applicable, then reboot into Safe Boot mode, and while there, attempt to switch into Dark Mode. If successful, then something that does not load in Safe Boot mode is causing a conflict during normal boot. Reboot normally, and then attempt to switch between Light and Dark mode again. If it is now working, then something was stuck in the System caches that Safe Boot cleaned up.

Otherwise, it might be useful for you to run EtreCheck and post those results from the clipboard into the Note tool on this editor's bottom toolbar. It is the third icon from the right that looks like a document. EtreCheck will not reveal any privacy information, but save us twenty questions about what you have and what you have installed.

You have a considerable amount of conflict candidate software installed. I would completely uninstall the following, reboot, and retry switching between Light and Dark mode:

1. All traces of CleanMyMac and CleanMyMac 4
2. All traces of iStatmenus
3. All traces of Wall Paper Wizard
4. All traces of MacBooster 7
5. All traces of Bandwidth+ (it is a menu extra)

Remove the above one at a time, reboot, and try switching to Dark mode. If you are successful, then you have isolated the conflicting product. The only malware detection tool that we recommend, and use ourselves is Malwarebytes for Mac. It does not get tangled up in the built-in security of the operating system. Malwarebytes is a fully functional, realtime malware detector for 30 days, and then you run it interactively for free. There is an optional subscription program if you want the real-time feature reinstated.

CleanMyMac has been reported to be overzealous in its cleaning process and taking out parts of the operating system, and applications. If this is the case, then you may need to reinstall the Mojave 10.14.3 Combo Updater to put removed, or damaged files back.

Completely uninstall cleanmymac, then try running the 10.14.3 Combo Update, in the hope that it will restore any corrupted or deleted system files.

If not, then you should do a clean install.