Bugman, when I first saw the Seinfeld finale, I thought the same too. However, after rewatching the series several times over and then finale as well, I think the finale was actually poetic justice for the main characters.
Think about all their actions during the series: awful, selfish characters who would ruin other people's lives with their impulsive, careless behavior, often in comical fashion. The main characters would almost never suffer long term consequences for their actions. Wheelchair lady, Susan's death, the bra-less wonder, Abu and the immigration debacle, just to name a few.
The ending of the series delivers that irony right back to Jerry, George, Elaine and Kramer. They are getting what they deserved for so long. To be removed from society for being such awful people. I thought it was hilarious.
Could the ending have been better? Absolutely. But I don't know how you would end such a fantastic show that was so hilarious, despite the fact that NOTHING ever happened in every episode, as that was its premise lol.