Because there isn't realistically anything that the RCN or Govt can to do Irving right now to actually speed up delivery timelines. Irving is still actively finishing up the final two CCG AOPS and actively working on the first River class, the yard has to clear out before work on the frigates can increase. Trying to set up another shipyard to take Irvings work at this point is going to take years and is legally dubious, given how Irving is the sole contracted combatant shipyard under the NSS and places like Davie are not capable of such work/prepping for their own Govt ship contracts in the near future.
They have been pushing in various aspects, chiefly being the removal of a bunch of non-US hardware from the design and being replaced with US counterparts to avoid integration concerns with AEGIS. Any way they can attempt to further meddle in the construction system right now is just going to slow everything down. You can't just say "make this faster" and expect them to do so, that isn't realistic.