Monaco and the Indy 500 are very different animals.
To boot, the latter has often become a very different animal over the 122 years that it has been held. Personally got into racing because of it, when Mario Andretti won in 1969, and although I was distantly aware of F1/GPs, it/they didn't seize my interest until the mid-1970s, when Mario fully switched over.
At that point, I became equally enthused about the two races, and it remained that way for lo 20 years.
When CART took it over, the 500 was still good, but as most know that series and the Indy series went into a major decline, so that affected my take on the Big Race in Indianapolis too. In a sense, there was a kind of poetic justice when the USGP race at Indianapolis in 2005 became the most shambolic event in F1 history. 
As Takuma Sato's fortunes rose, my interest in the Marecan race came alive again, and I was werra heppy that the Japanese driver won it.
Then there was another gap.
This year was the first that I watched both in a while.
***
Re Le Mans
It held my interest in the 1970s and 80s, but not since.
EDIT: This might have been a source of shame before I became at peace with my fogeyness, but I fear it's too late for that. 
Edited by Zmeej, 29 May 2023 - 21:09.