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Most likely issue is that you didn't delete all the mods. You could try deleting all files in rdr2 installation folder except folders and those ending with .rpf, then verify files while running whatever launcher you own the game on as admin.
If still doesn't work, could try renaming R* games folder in documents (also uninstall onedrive if you still have it) and try yet again, while once again running that launcher as admin.