If anything I found the later seasons more disappointing than 1 and 2 as smaller scale stories are replaced with moving the big plot forward, which still feels rushed somehow.
With season 4, I believe what happened is that towards the start of production JMS was told there would be no S5 after all, so he put all of S4 and S5 into S4 ... but then there was an S5 after all!
This is pretty common in TV shows, from what I've noticed. It takes a few seasons for a show to find its footing.
In the end, season 5 was given the go-ahead, and so now season 4 seems rushed needlessly.
(History repeating itself, and Babylon 5 being cursed to ironic timing, the WB Network and UPN eventually remerged to become The CW. A Babylon 5 reboot project development was started at The CW this decade, just before WB Discovery decided to get out of the broadcast TV business and start a fresh divorce at The CW somewhat resembling the PTEN divorce.)
[0] https://en.wikipedia.org/wiki/Prime_Time_Entertainment_Netwo...
An example not quite off the top of my head is as early as Episode 2 "Soul Hunter". It's a goofy plot full of weird pseudo-scientific mysticism with a "special guest of the week" who basically never returns (excluding books and movies), so in most shows meets several definitions of skippable, but this episode also introduces Dr. Franklin, has several key Sinclair and Garibaldi moments, provides background lore for the Minbari and foreshadows certain Minbari things to come.
That's just the second episode of the season. (Truly a rough start for some.)
Another common example is "TKO". It's a silly boxing match episode, much of it doesn't do much for the series except set up some of Garibaldi's goofier side and maybe foreshadowing Garibaldi's flaws. But it's also the Ivanova confronts grief and her heritage episode, a key part of Ivanova's arc.