Yeah Brian Wilson solo is kind of uninteresting overall. I do love that 1988 s/t solo album but I can understand if people don't. It is VERY 80s slick overproduced, with annoyingly loud booming drums, a lot of echo and fake keyboard tones. It grew on me over time. I kind of love the sound now but can't imagine its for everyone.
I never heard "Sweet Insanity" all the way but that might be worth hearing out of curiosity. It does have that awful infamous "Smart Girls" track where Brian raps though.
"Your Imagination" sounds like slick 90s adult contemporary, but a few songs are good. Worse production than the debut though.
Then there is "Orange Crate Art" (collab with Van Dyke Parks in the mid 90s) which has a great title track but kind of just gets monotonous and samey after awhile. Not really familiar with it all the way through though.
Then there's SMILE which I'm sure you know and love. The best thing he ever did solo obviously.
and "Gettin In Over My Head" which is pretty decent, and "Lucky Old Sun" which is one of his better ones. Most of it ends up just being "Okay" with mediocre production and arrangements but solid and decent songwriting.
I guess it is good to start with the debut and go from there. Seems like the debut has songs that come anywhere close to anything I really love as much as any good Beach Boys album ("Rio Grande" is actually brilliant.. amazing track and the best thing on the album.. def worth hearing for that. It's a suite like the old days but its actually done pretty well).