Pre-orders are only "bad" in the sense they further open consumers up to be exploited. Regardless, the intent to exploit consumers in the first place is the problem. I get what you're saying though.
This is the core of it, but there's a very simple reality concerning any sort of sale that will never change:
It's up to the consumer to decide the value of something for themselves and whether or not they want to spend money on it.
That's the ultimate consideration that determines whether something will or will not sell. No one can "force" a consumer to buy a game they don't want to buy. No one can be "manipulated" to do anything if they're making educated purchases. Value cannot be "dictated" from the outside. In the end, if people do not want something, they will place very little value on it, and no one will purchase it. Conversely, if something is viewed as valuable, then it will sell, even if it holds no practical value.
Supply and demand. That's all it is.
I would argue that buying anything sight-unseen is the same thing as making an
investment. An investment is not a purchase. Everyone can argue the semantics of whether a pre-order for a game is technically a purchase because an actual product will eventually be delivered...but there are split hairs all over the place. The simple fact is: "it is a purchase of something that does not yet exist." By direct, academic definition of the act, that's an investment. If I put money into something that is not complete and may or may not be successful in the end, then the value of my investment may or may not see a return. Hence, if I'm not willing to take that sort of a risk, then it would be really unwise of me to intentionally put money into something that hasn't even arrived on the market, yet.
Conversely, many pre-orders add value that cannot otherwise be attained in the form of exclusive content and other merch. So that's plenty of value for many people that are into collecting and have the money to burn. It helps to fund the project, and may result in a lot more being possible than would have been, otherwise. Yes, it could be viewed (subjectively) as "exploitation" of the consumer base, but that's the heart and soul of capitalism. The practice also helps smaller studios gain both funding and visibility on a market that is extremely saturated with very competitive products.
However, in the end, any arguments for or against pre-ordering, for whatever reason, are moot. If consumers continue engaging in the practice, then demand will be high and supply will continue. If people leave it, then either value will be increased to make the option more appealing, or the practice will be abandoned.
And, at all times, we have total control over what we spend our money on. Educated purchases.