Season 7 of overlap with Star Wars Episode III - Revenge of the Sith. This is an important tie-in that requires a lot of preparation. Extraneous stories originally planned have since been left out, one of which would have elaborated on a line from Yoda about his connection with the Wookiees.
The clone war enveloped the entire galaxy. As the conflict wound down, Jedi commanders were stationed across the stars. Most planets became entangled in the fight, including the Wookiee-occupied world of Kashyyyk. This is where Master Yoda would choose to lend a hand. As mentioned in Disney+ release of season 7.
Following the cancellation of The Clone Wars, Bad Batch would have arrived to help, which the natives would be hesitant to accept. The arc would have expanded on the mythology behind the Wookiees. There would be time devoted to their beliefs and spirituality. Eventually, the two parties would find common ground and combat their enemy united. This narrative would add depth to the Grand Master's words in the prequel. It would even include Tarfful and Chewbacca, who helped Yoda escape the planet in the film.
The Clone Wars has done a lot for throwaway lines in the films. Especially in the case of Revenge of the Sith, the context for even minuscule lines has been retroactively added. For the first 4 episodes of the season, the Outer Rim Sieges have gotten serious coverage, but the same will not be said for Yoda's time on Kashyyyk. The decision to abandon this arc was a matter of time. With this being a shorter and finale season, there are only so many episodes to fill. Disney opted for a leaner run as opposed to the initial plans.
On one hand, it is understandable why this arc was cut. It stands on its own and is by design fairly self-contained, though it would have been great to see Yoda and the Wookiees team-up. However, going without it is not a huge loss. At the same time, this story could have been so much more. It would have expanded on a whole handful of scenes from Revenge of the Sith, and added to the entire battle of Kashyyyk. Not to mention it would have made the already heartbreaking Order 66 sequence more emotional. After all, that is where Yoda was stationed when the command was given. Although if Disney+ is willing to finish up unfinished episodes for season 7, maybe some of these unfinished arcs can find a home as a mini-series or animated film one day.