Teleport is not realistic but reality is reality. People get lost. The elephant in the room is that ships during the period were not triremes that needed to be in sight of coastlines to navigate. They had advanced and sophisticated navigational techniques that could give a pretty reliable indication (not GPS level, people, but surprisingly accurate) of where they were on the map. From the captain's perspective, this was generally transparent as he has a trained crew that would periodically measure speed, 'turn the glass' (i.e. hourglass) to keep track of time, measure noon azimuths to ascertain latitude, and record sunrise and sunset times which were used, in conjunction with copious charts and maps, to reckon position on the earth reliably. The captain wasn't involved in this very much at all (although there were captains that were also excellent navigators.) That said, the fix is easy and could add a lot of content. Consider a system where you could see where your crew thinks you are on the map. The crew could be aware of some level of uncertainty (e.g. you have been sailing for two days under overcast skies) and could present you with an enlarged circle instead of a pip to show probable location. Or, your crew might think they have a perfect reckoning (showing a small circle or pip on the map) but really be off due to lack of crew quality or other factors. Consider the following possibilities:
1. Situational variables that reduce accuracy like overcast skies or the presence of grog rations on the ship (What? The scallawag got drunk, fell asleep, and didn't to turn the glass? He doesn't know how long he was asleep? I'll have him flogged...)
2. Maps of varying quality (and completeness) that you can buy or even craft (using Precision Instruments.) The accuracy of the maps could be based on your own navigation ability or on the quality of a potential navigation officer upgrade once officers are implemented.
3. General crew quality or even more granular crew quality metrics (which likely ties closely with officer upgrades for gunnery, navigation, supply, etc.)
4. Storms that really throw things off
5. Instrument upgrades that could reduce uncertainty, like precise hourglasses or exceptional sextants
Still, at the end of the day, with clear skies and routine crew navigational duties, a captain of the time would have some idea of where his ship was. More in-game features are needed to do this in such a way that it's not 'GPS' style, navigation should be part of the game. But navigation was definitely NOT sight-of-land only; people that are clamoring for historical accuracy by saying you should have no idea where you are on the map are flat out wrong. Captains of the era could anywhere in the world in open ocean with a clear day's noon and a sunrise or sunset could get a pretty good reckoning of their location within a miles, and they were limited only by the quality of their maps, instruments, officers, and crew, all of which should be in the game as these factors were just as critical as the size of your guns or speed of your ship.
Until more of these features roll out, here is a suggestion: Get rid of teleport altogether and replace it with "Get bearing to nearest friendly port" It could then appear as a blip on your compass and let you find your way back at least toward civilization. Keep it at a four hour cooldown and let the "power" expire in one hour. You could never get hopelessly lost using this, and there would still be a bit of a penalty for getting lost, but then players couldn't load up on cheap gold in Bermuda or somewhere far-flung and just appear at the capital minutes later. This idea would also mitigate the artificial population concentrations at capitals and encourage more re-basing to different map regions. Everything would be all game-time sailing, which is as close to real-time as we will ever get.