What a coincidence. I just started playing Saints Row 4 a week ago and I'm almost done with it.
To answer your question, no. I love how crazy things things got and I love how the characters reminisce about the things they did prior to Saints Row 3. Being more serious would be a detriment to the franchise. I don't think it really needs to get more insane than it already is but keeping it at that level is great. This is a game, since Saints Row 3, were you do end game level stuff in the first mission. I also love how the characters question the logic of everything going on and the answer just being "You're questioning this but not everything else?"
I agree that the wacky-crazy factor is a good thing, but I think the problem a lot of people have with SR4 is more the scope of the craziness.
As much as I loved SR4, I did feel a lot less connected to the Saints as a group in it, compared to the previous games. It's hard to feel invested in this small group of characters when their whole world is at stake.
I say keep the craziness, but I would also like to see them pull the story back to somewhere more personal to the Saints.
I think this game was a little rushed. It was obviously meant to help prop up the now dead THQ but when they were bought by Deep Silver why not finish it? I agree it could be pulled back a bit. The best parts of the game isn't really the gameplay, as good as it is, it's the interaction between the characters. Hopefully Kinzie remains part of the main stories. She has come to be my favorite character.