Matthew 23:1-2 is not a blanket, absolute endorsement or approval of Torah-keeping by Jesus. The tactic is to point to something new beyond Torah, although not completely detached from it.
But first, note the seat of Moses is a metaphor for the scribes/pharisees responsible for teaching the people what Torah requires of them. Yet, the rest of the chapter stands against Torah-observance, starting with the many Woes.
Hence, Jesus here and elsewhere repeatedly argues, corrects and even threatens said Torah teachers. In Mar 12.38; Luk 20.46 he declares without any qualification, Beware of the scribes! Period! And later in Matthew Jesus clashed with Torah teaching when it comes to the sabbath (12:1-14), purity laws (15:1-20), and marriage/divorce (19:3-9).
Lastly, in Matthew 23:34 Jesus prophesies:
Because of this, I am sending you prophets and wise men and teachers. Some of them you will kill and crucify, and others you will flog in your synagogues and persecute in town after town.
But, why, if the teachers of Jesus remained Torah-observant?
