Good boxers know about the jab and cross. They know how they will use the jab and cross, and when they are appropriate. They have a number of methods of training the jab and cross. Within a match, the jab and cross occur naturally, and "fit" when they do occur. The jab and cross can be executed under pressure in the same way that they are in light training.
Can aikidoists say the same thing about ikkyo or the various blends to yokomen uchi?
Would a boxer have as many opportunities to use the jab and cross under pressure, if his opponent had a bokken? Would he have the motivation to use them?
IMO, there's an elephant in the room: tai sabaki (called "footwork" by boxers). Here's a clip of Bas Rutten ranting about things he knows nothing about. Specifically he refers to yokomenuchi blend and ikkyo.
At ~25 seconds he says that stopping a (haymaker) cross punch and that dodging a jab to get the ikkyo grab (he leans back) just don't work. Actually he's right, but it's a straw-man argument because that's not how the techniques are supposed to work at all. At the end what he's saying is that failed execution of Aikido techniques are not effective. Duh. Ironically he does seem to be a fan of kotegaesh, never mind the same "footwork" which gives your kotegaesh power will get your face away from a jab.
I'm a short guy. With weapons (tachi dori: yokomenuchi ikkyo/kotegaesh) if I don't get the taisabaki right, I don't get any opportunity to execute the technique. If I don't move at all I might get whacked. It's great for learning timing skills (sen-no-sen, kokyu) and taisabaki which translate directly to unarmed techniques.
IMO, the weapons training is foremost (as a beginner, first things first) a crucible for developing and testing fundamental skills which apply to many techniques and arts. I have a friend who is learning and playing a lot of tennis. The fundamental skills are even similar in other sports.