I agree with you. I'm not saying infusion is perfect but it is a darn sight better than your gear being stuck at whatever level you get it. (AKA Vanilla Destiny) Etheric Light was simpler but also a one and done. It felt like a patch or a transitional step, which is exactly what it was. With Infusion there's supposed to be a progression and I can appreciate what Bungie is trying to achieve with it, even if they didn't execute it perfectly.
The downside is that it frustrates us min/max folks as we are forever looking for more infusion material. Also, that 80% rule is a bummer. No argument there.
A better system for infusion would have been where every items increases the XP bar on the weapon and higher light items increase it more. That way we can feed with whatever blues we want as we play. Now, the majority are trash.