I really wish consumers understood how produce works. :-(
There is no single food called "a Jalapeño". In the Solanaceae family, in the Capsicum genus, in the annuum sub-genus, there are dozens of hybrid and cultivar fruiting plants, which are all referred to as "Jalapeño". They all have different properties in how they grow and what they turn into. This includes taste, size, color, shape, and spiciness. (https://www.thechileman.org/results.php?chile=1&find=Jalapen...)
If you want to buy "a Jalapeño", or any kind of produce, and have a reliable experience, you can't just wander into a random store and pick up a generic name for 40 different cultivars, made god knows where and how, shipped to your neighborhood god knows how, and expect that the thing you selected is exactly what you wanted.
Imagine you want a burger. You go to the Big Burger Mart. From a giant bin labeled "Burger", you pick one Burger. You take it home and eat it. Will it be the burger you expected, from the place you expected, tasting the way you expected? Maybe not! But it's An Burger! You didn't seem to care what kind of burger it was when you picked it out of a big bin called "Burger". You didn't ask where it came from, how it was prepared, how long it's been sitting there, etc. So you can't really expect anything but "Generic Burger", which personally doesn't sound very tasty.
To get the produce you expect, you should buy a specific cultivar of produce from a reliable producer. And you're probably gonna need to buy it locally, because the food logistics chain delivering a pepper from Chile all the way to Nebraska is not going to result in an ideal pepper. Another way to get what you expect is to grow it yourself. Many jalapeño cultivars (and other peppers!) grow well in containers. If you want to skip the whole gardening thing, you can buy a pre-grown bush of jalapeño online from a nursery like Bonnie, and just keep it alive and enjoy fresh peppers indefinitely.
I actually feel bad for the supermarkets. They have to read the minds of customers that demand so much, feed back that information to growers about what to grow, and then get it into the stores, with 365-days-a-year perfect consistency, unblemished, "ripe", and tasty. It's an impossible task. Yet they pull it off, even to the point that people have grown up their whole lives not knowing what it is they're buying or how it gets into their shopping cart. But that doesn't stop people complaining about it.