The Klingons have been missing from live-action since Star Trek: Discovery season 2, which shows just how much damage the series' reimagined Klingons did to the bloodthirsty warrior race and their place in the franchise. The Klingons, in their most popular 24th-century incarnation, still are a regular sight in Star Trek: Lower Decks, and season 3 even featured the return of Chancellor Martok (J.G. Hertzler). Yet the wait to see the Klingons return in live-action on Star Trek: Discovery or Star Trek: Strange New Worlds seems to have no end in sight after the number Discovery did on the Klingons.
In truth, the Klingons have been redesigned before. Star Trek: Deep Space Nine even joked about how the change from the more human-like way the Klingons looked in Star Trek: The Original Series to their armored, wild-haired, and bony-forehead appearance in Star Trek: The Next Generation was something the Klingons "do not discuss with outsiders." But when Star Trek: Discovery season 1 redesigned the Klingons (many Trekkers felt unnecessarily) to be hairless and appear even more alien, the uproar was significant. As a 23rd-century-set prequel, Star Trek: Discovery caused issues with canon, and the Klingons were one of the least popular aspects of the series, although Discovery also laudably introduced the first female Klingon High Chancellor, L'Rell (Mary Chieffo). After Star Trek: Discovery season 3 shifted its setting to the 32nd century, its version of the Klingons haven't been seen since.
It's notable that Star Trek: Strange New Worlds, which is set just a couple of years after Star Trek: Discovery season 2, hasn't shown the Klingons. Granted, Strange New Worlds is focused on introducing new aliens and planets to canon, and the classic alien species the series has re-imagined is the Gorn. A future version of Admiral Christopher Pike (Anson Mount) mentioned the Klingons and brought a time crystal in Strange New Worlds' season 1 finale, but the question of which version of the Klingons will be seen on the show remains unanswered. It seems that outside of Star Trek: Lower Decks, the Klingons are a persona non grata alien race with the live-action Star Trek series wary or unsure how to deal with them post-Star Trek: Discovery season 2. Even Star Trek: Picard seasons 1 and 2 had no dealings with the Klingons at all, although that's about to change with Picard season 3.
Worf's Picard Season 3 Return Won't Address Star Trek's Klingon Problem
Worf (Michael Dorn) returning in Star Trek: Picard season 3 will be the first live-action sighting of a Klingon since the USS Discovery left the 23rd century behind. Worf's comeback will answer some important questions about where he's been since Star Trek: Nemesis, and it could also address the state of the Klingon Empire in Picard's early 25th-century timeframe. While it'll be exciting to see Worf again, his comeback won't address the lingering issue of the Klingons' status in Star Trek: Strange New Worlds' 23rd century or in Star Trek: Discovery's 32nd century, where there has been zero references to the Klingons even after two seasons of Captain Michael Burnham (Sonequa Martin-Green) reuniting the broken United Federation of Planets and meeting that era's Cardassians, Bajorans, Ferengi, Romulans, and Vulcans.
It's quite possible that rather than finally fixing its Klingon problem, Star Trek: Strange New Worlds and Star Trek: Discovery will continue to simply avoid the Klingons for the foreseeable future. Strange New Worlds could easily leave it so that after Star Trek: Discovery season 2, the Klingons aren't encountered again until Captain James T. Kirk (William Shatner) faces them on Organia in the TOS episode, "Errand of Mercy," which was the Klingons' first Star Trek appearance. Star Trek: Discovery could also keep on ignoring the Klingons in season 5, but this would be unfortunate because it would only compound the problem Discovery created with its ill-conceived revamp of the Klingons in the first place.