You can rarely go wrong with black text on white.

For an example of how to make a simple presentation look good, the "Death by Powerpoint" slides [1] show how to do a good job.

[1] https://www.slideshare.net/thecroaker/death-by-powerpoint

Consider at least keeping a logo in a corner, or perhaps as part of a title bar on each slide or a few key slides (title, intro, outro, first in a section). It makes it seem more official (should be a minor thing, but can be impactful depending on the audience). When presenting to peers, my simple presentation slides were appreciated and accepted. When presenting to management or other teams, I had to make those additions or it was thought of as a draft or hastily assembled.

Its the details that matter. A small company logo on every slide, color scheme that matches the company colors, and not having things too crowded (a la Death by Powerpoint) tends to make things look more put together.

Is there something that makes this a battle worth fighting? Good luck.

This was my reaction as well. If you have company-provided presentation materials then use those. What benefit is there in not doing so?

The templates are too busy and makes adding content difficult, especially when some will see them in lower quality over poor lines. It's not really a battle since no one is really objecting.