Will untinned wire and the usual crimping suffice in many cases? Probably, given that many wires on many "good old boats" are original.
Only for a while. When I bought my boat, one of the notes by PO was "well, the ceiling above the sink gets a bit warm and the light does not work, but thats no big deal"
When I opened it I realized that electrical fire was perhaps days away. This was the case in a number of locations on the boat. Old wiring on old boats, if untinned, is a disaster waiting to happen. Perhaps the main reason that these fires don't happen more often is that electric systems on these boats are often so neglected that nothing works
Non-tinned wire will be dangerous on the boat in 10-15 years (and 15 year old boat is nowhere near it's end of life, presumably).