I have sat in this seat several times.
As a result of their confusion, they tend to make uninformed decisions that lead to major headaches for everyone, or they simply fail to use the system effectively.
The problem here is pretty straightforward:
they tend to make uninformed decisions
Firstly, I'm going to assume this is the case. You have to handle this very carefully - assuming someone is incompetent when they're just busy will not endear you to them in any way.
So, let's assume they're uninformed - the problem simply stated is that they need to be informed. That means somehow inserting yourself into the decision making process they undergo and listening to what they want to achieve.
Then, and this is crucial - lay out all the options, presenting as simply as possible any technical concepts that you need them to know and answering any questions, then let them decide. They'll still have made the decision - they're still in charge - but you've armed them with the information they need to make the right decision.
At this stage, I should say what we're trying to do is guide them, however, one thing I've taken out of doing this almost all of my working life is that sometimes when presented the options, the manager picks one for business reasons such as speed, cost etc. As IT people, particularly programmers, we tend to be set in our ways in terms of "technologically best", whereas the manager may see things business/strategic viewpoint. Don't begrudge them this; it's the reason we're still employed, after all.
Now - how to insert yourself into the decision process? Well:
... as they're very busy
Bingo. Offer to save them time. Find an example of a technical solution you think isn't the best one and contrast it with one that works, explaining how that'll save time or money (or both) all around. Then, and this is tricky - either try to offer to look at decisions, or if the manager will not let go, you can try to involve yourself in the discussion until your frequency of attendance ends up including you by default.
As I say, the important aspect here, tempting as it is, is not to presume, and make the decisions. Interpret the requirements and present the options. Think "technical liaison". Also be aware sometimes, in some company cultures, the idea of receiving advice from junior staff doesn't really exist and you may not be able to affect the influence you need to.