I agree with your points around not preordering, or waiting for reviews etc. However, I disagree with you that refunding after 10 hours isn't the right thing to do for a few reasons.

First, the size of the game in question. For a short, 10-20 hour story driven game, a refund beyond 2 hours is ridiculous. For a large, open role playing game, where somebody spent 120 AUD expecting to get 50-100+ hours of gameplay, 10 hours is perfectly reasonable if you're really not enjoying the product. If I can send back a meal at a restaurant that I've had (relatively speaking) two bites of, I should be able to refund a game the same way.

Second, again speaking for Australia as a jurisdiction, is the behaviour of brick and mortar stores. I can purchase a physical copy of a game, play it non-stop for two weeks, and get a refund. They have no way to know I finished it three times, but strong consumer protection laws enable me to game the system like this. I agree that it's the wrong thing to do, but Steam is aware of the fact that the same consumer protection laws apply to them. While they have enough information to stop people from outright gaming the system, Steam needs to balance that against driving people to other storefronts or back to physical retailers.

Finally, your premise that people can't reserve the right to get a refund just because they don't like something. I would agree with this, if game demos were still a wide practise. I can't get a change of mind refund on a shirt I buy in a physical store most of the time, but I can try the shirt on in the store to see how it looks on me. I can get a change of mind refund on most shirts I buy online, because I have no idea how it's going to look. Yes, you can wait for reviews and watch gameplay, but it's always different when you actually play the game. At the end of the day, it still comes down to "I thought this game would be X but it's actually Y".

A firm, inflexible refund policy in my mind achieves the opposite of what you are looking for. If people can never get a refund because a game simply isn't what they thought, what barrier is their to a mildly successful company ridiculously overpromising, securing the bag, and disappearing into obscurity? If everyone buys the game on Steam and can't get their money back, the company has won in the short term. If 50% of preorders get refunded, the company has just lost all of that money.