Hahahahahahahhahahahaha
No.
First off, I don't get how the second half of the season can look "sketchy" and "not right" and "basic" at the same time, so I'm going to ignore that misstep in language. Second off, while the animation is not "film quality" (and why on earth is that a detractor? SpongeBob is a show, not a movie), it is without a doubt the best animated Season with the best designs, loosest animation, and greatest drawn boards. Even if you dislike the off-model designs, every character moves so fluidly, is animated in such a loose style, that it absolutely destroys every Season that isn't Season 1 or Season 9.
SpongeBob is a show with very intricate designs, designs that are hard to draw (characters like Sandy and Squidward are very hard to draw well), and even harder to animate. Season 4 took the characters, and made them 20x more expressive. They moved 20 times better. SpongeBob became smaller and the lines became thicker, but why is that a problem? Yeah, SpongeBob looks like White American cheese instead of cheddar, but that's because something was up with the digital ink at Rough Draft around this time, the same thing is evident in Mandy's hair in "The Grim Adventures Of Billy And Mandy". Season 4 took the characters and moved and animated them wonderfully in ways no Season has done since. Squidward's breakdown near the end of Driven To Tears, his insane expressions in Skill Crane, are staged in such a way that it's pushing the way the character moves and acts in a way that only can be done in animation. SpongeBob's expressions in Have You Seen This Snail, Patrick's expressions in Patrick SmartPants- they're so expressive, and it's so much better than the 5-7 era where we got the same 5 expressions for every character and everyone moved in the stiffest way possible. The sequence in Ghost Host at the end is probably some of the best animation and direction I've seen in a kid's cartoon.
Yes, it's off-model, but not in a bad way at all. The designs are simpler, not worse. No other season has been able to rival the expressiveness and fluidity and overall solid level of art and animation being cranked out at that time. If you just personally don't like it, then whatever, but from an objective "good animation" standpoint, Season 4's animation is great. Best of the show. Hands down, only Season 1 and 9 can stand up to it.
don't be talkin crap about animation man you will get killed every single time