Variety is important. There are varieties like False Alarm, Fooled You, Felicity that are as as mild as a standard bell pepper. TAM Mild has just a touch of heat. Most people prefer the taste of green Jalapenos, but when they ripen, the taste is bit smoother but heat is the same. I expect that you got one of the "heatless" varieties.

Depends upon what you are using them for.
Use green in salsa verde, use red and ripe in salsa rojo.

Jalapeno M has good heat for a Jalapeno.

Kevin

The mild ones I have planted are Fooled You Hybrids...

I'm not really concerned about the heat, and whether they are hot or not... My main concern with them is that they every one taste like a plain ol bell pepper. I've let them get fairly large, a little over 3" I just don't understand why they don't have that classic taste I was hoping for.

Does it need any nutrients to aid in the taste? There was a fairly small one that ripened to red fast, and even that had the same typical taste.

Could the weather be affecting it? It has been a fairly wet year this year here...

Oftentimes the first couple of pods have an off taste, mild, grassy or just different, etc. Try to reserve judgement after you've tried more from each plant, red-ripe pods and large mature green pods.

There is a chance that adding minerals to the soil will affect taste, like a good rockdust or azomite, but the effects may be mild and you wouldn't notice it in this round of pods, if at all this far in the season.

And finally, i do believe that overall climate can influence flavor, and this season certainly was unusual. I think it's more noticeable with tomatoes than peppers though.

Just my 2c