You've got absolutely no idea how complex our systems need to be. As it happens, we are implementing a new Sage based system ourselves and even paying for them to "put a rush on" we are most of the way through a near two year process. No off the shelf solution was suitable. Just because your business is simple, it doesn't mean that everybody else's is.
Ours isn't off the shelf either, ours handles multiple levels of stock inventory from raw materials, production stock, repairs stock, different levels of build, then it's split into commercial and military.
You then also have all our manufacturing drawings, BOMs, software control each with multiple versions and customer specific control.
You have manufacturing route cards within Sage also. Everything down to each screw and resistor is tracked and traceable for 10+ years.
Different customers pay different prices have wildly different terms and conditions all tracked and traced.
Yeah I don't know your system but from a simplistic view you buy and sell products.
We buy raw materials, manufacture, some items get part completed by a sub contractor then have to come back, be certified and start at the beginning again, we sell all over the world with different certification in each area.
We then do repairs on top.
I imagine it would be as if OCUK also manufactured everything they sell, from the absolute ground up, also repaired everything, dealt with obsolescence were contracted to support everything for 10 years, no parming warranty off on another manufacturer. Imagine if you sold a 3080 you'd have to still be able to make and sell that in 10 years.
So yeah I'm going out on a limb and saying it's a lot simpler.