Mostly by not being interested in the games. In my case, I wasn’t interested in the early reveals.
Just Cause 2 was fun and interesting, but it started to wear thin by the end. From most of what I’ve read and seen, neither JC3 nor even JC4 add enough to that experience. As for Project CARS 2, I have a ton of car games that I’ve never even installed; I don’t need another. Wizard of Legend looked interesting, but it wasn’t selling me the bundle on its own.
The rest of the bundle is bundle filler. I don’t mean that as in insult, but Humble had reasons to not try to use them as early reveals. Sometimes you can luck out and hit a late reveal that on its own justifies the whole bundle for you, but mostly these games act as sweeteners or justifiers. If you already liked the bundle, then these can make it an even better deal, or to push a questionable bundle into a valuable one. Not that it mattered to me in this case, because again the early reveals failed to sell me on the bundle, and I do not buy monthlies on just the hope that the late reveals will make up for more than a few dollars.
Regions of Ruin looks interesting, but I didn’t buy it when it cost less than $2. If I’d bought the bundle, this would still serve as that extra justification of value, though. Sundered is one of those games that interests me, but which I’ve heard/seen enough about to bump it into eternal wishlist material, that game that I never buy no matter how low it gets discounted (because it will most likely never see its price drop faster than my interest.) It is another solid sweetener/justifier. As for Q.U.B.E 2, I don’t believe I ever installed the first one, >observer_ doesn’t much interest me, and I don’t believe I’ve bothered with any Humble Original.
The thing about the sweetener/justifier titles is that their perceived value can be somewhat relative to the overall value of the bundle. If you like a bundle in general, or are even near the borderline on “value”, then you might inflate the value of these sweeteners. Conversely, if you are sour on the bundle in general, then you might deflate the value of sweeteners. If a bundle was strong, I might rate Regions of Ruin at $2 or $3, even though I wasn’t willing to pay $1.80 for it a couple of months ago. Or if I was trying to justify an accidental bundle purchase, or just trying to convince myself that an iffy bundle that I bought was worth the price, I might would rate RoR as $2+. On the other hand, if I skip a bundle that at best looked iffy, then I might under-value a title like RoR, saying I wouldn’t even buy it for $1, even though I probably would buy it at that price.