The words attributed to Jesus in Matthew 23 should be seen in the context of the tension that exists between giving attention to the normative commandments of the faith and the moral imperatives implied by the faith. This tension exist in all faiths such as Catholicism, Islam and Judaism, that have both fixed, normative commandments, and also have moral imperatives. This tension, and the polemics that spring from this tension, are a permanent feature of all of these faiths.
There is no evidence in the NT to suggest that Jesus intended to abrogate any of the Mosaic law in his lifetime (Matthew 5:18). That abrogation that occurred later, in the time of Paul. Furthermore, the normative Jewish position regarding the weight of various commandments at the time of Jesus was that we must conduct ourselves as if all commandments had equal weight, because we have no way of actually knowing how to ascribe relative weights to commandments. The second chapter of the contemporary "Ethics of the Fathers" states:
Be as careful with a minor commandment as with a major one, for you do not know the rewards of the commandments. Consider the cost of a commandment against its rewards, and the rewards of a transgression against its cost.
So, it would appear that the intention of Mathew 23:23 is to say that in the context of the social circumstances of the time, that more weight needs to be given to the moral imperatives of the commandments because without them the normative commandments don't make sense, but that there is no intention to state that the the normative commandments are inherently of lesser weight.
Note that the contemporary language of the Ethics of the Fathers itself recognizes a catagorization of commandments into lighter and heavier like the catgorizement thst Jesus makes, while at the same time indicating that we cannot use our ideas of lighter and heavier to discriminate between commandments, we need to fulfill all of them.