I have a feeling this job is not going to be a good fit for you. But I am going to try to give you an example of what "stay in your lane" means for you, and how you can work with the boss you have and the company you have.
So, let's take a simple example (and nobody pick at the details of it, because it is oversimplified for a reason.) Someone is doing a particular process by hand. It takes x hours a week/month and more importantly, y times a year there is a delay or mistake that costs z dollars or hours or customer goodwill or something. (Eg we reduce our bill 20% that month to make up for that mistake.) There's every chance that you don't know what the bad thing costs when it happens. That's the sort of thing it's your boss' job to know. You feel that technically, the right thing to do is to automate this process. It will cost a hours, and these other things will be delayed while you do it, but then all that hand-work time will go away and the expensive errors will go away. You see this as a technical decision, where you choose the "right" thing, and automating is pretty well always the "right" thing to do.
Your boss sees a different picture. The costs of doing it the way it is now, the possible increases or decreases in those costs over time, the estimated cost of your suggestion, the estimated benefit of doing that, and so on. The other things you and the other developer could be doing have to be weighed against it, of course. If that "number of errors" is very low, like one a year, and the boss can be convinced that "oh that was a one-off it won't happen again" then the boss is likely never going to decide to do the automation. If that number is very high, and the problems it causes can't be solved with money and time (disgruntled customers who leave) then the boss is very likely to decide to do it.
See how this doesn't really have a technical part? You're worried about "competence inversion" by which I think you mean that your boss should be more competent than you, but is in fact less competent. You may be right. From where I sit I consider another possibility: your boss has plenty of competence at a job that is completely different from yours and wants you to bring technical details that will enable making a business decision quickly and accurately. You want the boss to delegate those business decisions to you. But you don't seem to see any difference between a business decision and a technical decision. I wouldn't, therefore, delegate those decisions to you.
Relax. You don't have to do your boss' job. You don't really even know your boss' job. Provide the information your boss needs (this is industry-standard practice, this will save 5 hours a week, this will prevent the sort of error we had last month that took 3 days to fix, I think this is about a week's work) -- in a format your boss needs. Effort. Savings. Best practices. Risk. Non technical words. Business words. Your boss doesn't need or want to understand whether virtual inheritance or template meta programming are silver bullets or overhyped nonsense: bosses want business words. You can get those answers. Then the boss makes a business decision, and you implement it.