I cant play rdo

Only addons and Story mode are available in the purchase history and seems I cant use unless I purchase RDO.

Was wondering.. how populated is RDO..

Did you purchase Red Dead Redemtion 2: Story Mode, or did you purchase Red Dead Redemption 2 the full game?

Story Mode is just an add-on for Red Dead Online. If you had access to Game Pass games you could download RDO and then purchase Story Mode to play the single player. RDO has been removed from Game Pass. If you only purchase Story Mode, you will now need to purchase RDO to keep playing the single player.

So to wrap it up, to play the single player portion you need to have purchased either the full Red Dead Rredemption 2 game or you have to have purchased BOTH Red Dead Online and it's Red Dead Redemption 2: Story Mode add-on.

Story Mode is merely an add-on for RDO. It is not the full single player game.

Everything you have mentioned are the things I want in RDO too

Did you purchase the Story mode or the Online mode? If it is either, then you'll need the other one to play as each one doesn't work alone.

This is not entirely true. Red Dead Online does not need anything else to be played. Red Dead Online does not need Story Mode in order to play online. RDO is a stand alone game as well as being a part of the full game.
Story Mode is the only one that needs something else (RDO) since it is the only one that is considered DLC.