Squishy doesn't necessarily mean soft - tactile feedback is different to actuation force.
I used to have a Microsoft Multimedia Keyboard, but after half a decade of use, the keys became so stiff that it started hurting my hands to type with it. I tried buying one of the newer Microsoft keyboards to replace it, but the tactile feedback was so horrendous I returned it immediately. I bought a mechanical (Das) keyboard shortly afterwards, and it actually had a lower actuation force that the Microsoft keyboard, and my typing speed has improved significantly since I got it.
I agree absolutely that you need a decent keyboard if you want to type quickly, but I question your assessment of actuation force; I'd say it's more a matter of preference.