Warning: The following contains SPOILERS for Superman and Lois season 2 episode 12.
The problem of Superman and Lois ignoring the existence of Supergirl went from bad to worse in the season 2 episode "Lies That Bind." This is hardly surprising, as earlier episodes of the spinoff series barely seemed to be set in Arrowverse. Yet Superman and Lois reached new lows when Clark, faced with the need for a second Kryptonian to save the world, formulated a convoluted plan rather than call his heroic cousin for help.
Apart from a cameo appearance by Arrow's John Diggle, Superman and Lois has not had any crossovers with the other series making up the Arrowverse. This was originally due to the shooting restrictions brought about by the COVID-19 pandemic. However, even once the restrictions were lifted, the writers of Superman and Lois did not make any knowing nods to the larger universe, with the scripts for Superman and Lois routinely acting as if Superman is the only superhero on Earth-Prime and that there is nobody else the U.S. Department of Defense can turn to in dealing with alien invaders or natural disasters. This seemed particularly egregious in the wake of the series finale of Supergirl, where Kara Zor-El helped establish a new Department of Extranormal Operations (DEO) focused on dealing with the same threats her cousin faces in Superman and Lois.
This tendency to ignore Supergirl as a potential ally achieved new heights of ridiculousness in Superman and Lois season 2, episode 12, "Lies That Bind." Early in the episode, General Sam Lane and John Henry Irons approach Superman with their analysis of a strange energy-absorbing pendant sought by prophet turned Parasite Ally Allston. Their findings suggest that while Superman isn't powerful enough to destroy the pendant on his own, the combined strength of two Kryptonians could get the job done. This leads Superman to approach his imprisoned half-brother Tal-Rho for help, which inspires a side-trip to Smallville so that Tal-Rho can apologize to Lois Lane for everything he had done to hurt her in his secret identity of Morgan Edge. It's an overly elaborate plan, given Clark could have easily gone to Supergirl for help.
Clark's decision to ask Tal-Rho for help is seemingly the result of his recent trip to Bizarro World, where he encountered a version of Tal-Rho who had been a true brother to Bizarro Superman and worked with him to defend their planet. This Bizarro Tal-Rho helped Superman to escape back to Earth-Prime with one of Ally Allston's pendants, prompting Clark to try and reach out to his half-brother and offer him a chance to prove that he has the potential to redeem himself for his past crimes. While this is characteristically noble of Clark Kent, it's also completely nonsensical given that time is of the essence and recruiting Tal-Rho requires both convincing him to help and selling General Sam Lane and his other allies on the plan.
The lack of connections to Supergirl and the Arrowverse continues to be Superman and Lois' biggest flaw. Thankfully, showrunner Todd Helbing has promised to address "why we don't bring up Supergirl or The Flash or any other heroes" before the end of Superman and Lois season 2. This would dramatically enhance the show as, while it is only natural that Superman and Lois should highlight its title characters, the series' ongoing refusal to acknowledge the existence of Supergirl has become truly ludicrous.
Superman & Lois releases new episodes on Tuesdays on The CW.