I'm aware that this has been discussed many times in this community and I completely understand the rules but I have my own arguments against this theory.

Familiar Locations in GTA:

Everyone knows at this point that one of the most repeated arguments is "Both games share locations, Armadillo and Cholla Springs are in Sandy Shores". This might sound convincing but that group of people also ignore the fact that San Andreas State is outside of the United States of America, San Andreas in the HD universe is an island. Figuring out why R* named those avenues Armadillo and Cholla Springs is not a mystery. Red Dead Redemption came out before GTA 5 in 2010, and Grand Senora is a desert like Cholla Springs, simple to understand the reason (Reason: It's a reference). And I'm not counting Strawberry (GTA 5) because that place was named after Darryl Strawberry, who is a baseball player from Crenshaw, Los Angeles (real-life counterpart of that location).

UFOs in Both Worlds:

Another popular argument is that RDR and GTA have extraterrestrial elements, but how is that a solid evidence to begin with? RDR's UFO model is smaller and has a different shape in comparison to GTA 5's models (the black one doesn't count). And UFOs in RDR2 are also a reference to GTA 5, people seem to forget that GTA 5 came out before RDR2, it's obvious that there are going to be references to their previous games.