That policy assumed good faith on the part of the consumer. The original thinking was likely 'OK, if they return it after <timeframe> it's because it was a lemon/never worked right/etc' rather than for abusive reasons like 'TV returned right after Superbowl Sunday' (because they had their party and no longer need it) or 'returned laptop after 6 months' (because the school/work project ended and they no longer need it) So the assumption baked into the policy was that buyers wanted to legitimately own the thing they purchased rather than using the refund policy as a way to get a free short/intermediate term lease.

You seem to be saying 'well they did say any reason' and that good faith on the part of the buyer didn't/shouldn't enter into it. Yes they did, and people behaved the way they did. Now the generous refund policy no longer exists. See how that works?

The policy even assumed some amount of semi-bad faith behavior, the thinking was their return policy was also a bit of a charity program for the needy and destitute[1] (a Costco member lost their job and so returns a bunch of items for cash, etc). What they didn’t anticipate was the sheer number of people who began acting in bad faith (and the deflationary nature of electronics making it especially tempting), it was too much to bear.

It’s a shame the policy is gone. There was really no peace of mind quite like it, knowing that if your device failed after years of use, but still due to a defect, you had recourse. And for poor people, it was a godsend of a program especially (and not because it could be abused, but simply Costco providing a service that anything you buy will work as advertised)

[1]source: some internal training I received back in 1998

Yep. The same thing happened with LLBean. They used to offer lifetime returns/warranty replacement on all items, which worked when people acted in good faith. After many decades of this policy, a gray market of used LLBean items emerged, people would buy multi-decade-old used LLBean items, then "return" them as worn out for a new one or even a full refund. It became a whole cottage industry, and they now have a one-year limit on their any-reason return policy.

People suck, especially when they are disconnected from the human side of business.