I mean, it's got 4 pages of instructions for whether you should file it at all, and if so where to send it. It's got a third of a page for what to put in the "name and address" fields. It's got half a page for what to put in the "SSN" field. A bunch of that deals with edge cases that are not relevant to most people, who don't even read this part of the instructions and just write down their name, address, and SSN.

8 pages of EIC credit table. 10 pages of tax table. Longish, but pretty simple.

Now there are in fact things in there that are not simple. Filing status is usually simple, unless you try to figure out "head of household", in which case it's not. But in general, the 1040 is quite simple as tax forms go, and the instructions are mostly long because they are written out with a lot of detail and to be easy to follow, and have to cover various edge cases.