IHC is bad also. Just an exploded drawing, IIRC. Though some kits are so simple, that is generally enough.
The Walthers seem to be the best as far as instructions go for mass-market plastic kits. At least that's been my impression. But, having said that, the best instructions are usually the craftsman kits, like the laser-cut wood kits.
A have a number of building kits that are sitting unbuilt (what a surprise!). Mainly because there's no real room on my current layout for them. But, when I get around to building the big layout, there should be space. Presuming those buildings are still applicable.
I get a lot of buildings off of eBay. Some interesting stuff, which are specific fits to specific needs. Same with the stuff I get from train shows. I'm being careful because I can easily have more buildings than I can use on the big layout.
I have a lot of Walthers modular, and DPM pieces as well, to fill in the gaps. Those don't need much in the way of instructions once you get used to how they all go together. And, be prebuilt buildings need no assembly either, unless it's to kitbash or detail.
Kennedy