Season 4 feels so packed because the show actually got cancelled between after season 3. They got to do the 4th season, but the 5th one had to go. The result of this was that the two big main storylines that had been building tension since s1, aka the Shadow War and the Earth Civil War, which were originally supposed to be wrapped up over the course of the 4th and 5th seasons, instead both had to be condensed, crammed into and finished during the 4th season.
Then after condensing the preplanned main story into s4, they got picked up again by another studio to do season 5 after all. The problem was that the story that was supposed to be in s5, had already been done, so s5 was kind of made up as an afterthought when they got there. Sleeping In Light, the final episode of season 5 and the ending of the show, was originally filmed as the finale for s4. That's why the actual s4 finale is this weird timeskip thing of somebody watching the historical record about humanity from faaaar in the future.
Yeah, you have tons of conflicts that just come and go in the last two seasons.
You have the Shadow War, Mimbari Civil War, Earth Alliance Civil War, Centuari War leading into the Drahk war, and the Telepath War all hitting points in the final two seasons.
Peace is a lie. There is only passion. Through passion I gain strength. Through strength I gain power.
Through power I gain victory. Through victory my chains are broken. The Force shall set me free.
–The Sith Code