Is there some app that makes this easy? I'm guessing the answer is "no", given that all of the search results are for malware "Free Online Tools" spam sites.
The only way I know of is with ffmpeg, but the syntax is incredibly tedious and time-consuming to create: you need to type in the rectangle in pixels, and the start/stop time in seconds. To do it for one across the whole video is awful:
-vf "delogo= x=1640 :y=3 :w=270 :h=90 :show=1"
but to do more than one, or to add start and stop times, it's completely bonkers:
-vf "delogo= x=60 :y=310 :w=180 :h=120 :show=1
:enable='if(between(t, 11, 22), 1, between(t, 219, 231))'"
(And you can't type those seconds as H:MM:SS, either.) I just want to drag out a rectangle with my mouse, and select the range on a time slider. Why is this too much to ask?
(And obviously I want this hypothetical tool to automatically recognize them, too. ENHANCE! ENHANCE!)