"Classic" Marathon is available for free on steam, Marathon Infinity and Marathon 2 coming soon.
https://store.steampowered.com/app/2398450/Classic_Marathon/
They state clearly that play time must be 2 hours or less to return a game. Just because you didn't adhere to those guidelines doesn't mean they are bad with returns. Your current situation is entirely your fault.
This is 100% a you problem. Something is obviously broken somewhere. I've never had these issues with Steam.
I do agree competition is a good thing though.
If your patient, with games on Steam at least, there is more or less zero reason to ever go grey market.
Just wait for a sale. Ive picked up 80% of my library for less than $10 - you just wait for the sales.
Or you can choose to be impatient...
Get Space Crew: Legendary Edition free from Steam till 3-14-24.
https://store.steampowered.com/app/1176710/Space_Crew_Legendary_Edition/
You are a captain in the United Defense Force, captain of your own star ship. Recruit your crew, customise...