“Isn’t it more important to kneel in our hearts rather than with our knees? And even more important to keep this attitude of reverence for the Lord with us as we leave the Mass and go out into the world?”
I would prefer to kneel both internally and externally. While I would still kneel, I wouldn’t look askance at those who stood. I do look with dismay at the churches being built without kneelers.
I would prefer to receive communion kneeling, or genuflect prior to receiving. I’ve seen it done (genuflection) at my parish, and see receiving while kneeling occasionally at the daily mass I try to attend near work.
However, I think if I were to do it it would somehow be more disruptive than not, so out of respect for my fellow Catholics receiving at the same time, I stand.
With respect to kneeling in your heart - I compare it to smiling when you are not in a good mood. A smile helps bring about a good mood. Unfortunately there are times when my concentration wanders during Mass (today being one such day). Kneeling with my body helps my heart to kneel.