Out of the Ancient/Classical era bunch, Oracle is a pretty decent bet, if you attempt it after NC, failing it is not that problematic. But most of the times it's either long gone by then (Maya will get it if they are in the game), or you have a good shot. I have failed Oracle multiple times but it wasn't such a big deal.
Other than that any wonder that requires an opener which nobody went for is safe, but really only HG and Pyramids are worth it, SoZ is pointless (just conquer it) and Great Mosque is also useless on high levels.
ToA and Petra are a gamble, the payoff is good but both come with very high opportunity cost and if you miss them you are in trouble. I would only consider ToA with an OCC strategy, or at least an OCC start (I had a strategy with India, beelining the wheel to spam war elephants and building ToA while teching the wheel, but it is very risky and requires a good start). Petra is better since it comes later, but if an AI has a capital with desert you most likely wont get it. If you do however it is crazy good (provided you had the proper city for it).
Mausoleum of Halicarnassus is a very weird one, sometimes it's gone by turn 40 sometimes it is still available at turn 90. It is a fairly weak wonder, and unless you have 3 quarries around it's not worth it. The 100 gold you get when you expend your GP, not when it is born so if you keep a bunch of GSs around you will get 7-800 gold late game which is not that good. Early on it's a good boost and will probably give you 4-500 gold when you need it, but I don't think it's worth the opportunity cost.
Stonehenge, Great Library and Parthenon are off limits, I think you can get Parthenon if you beeline it (but why?). Great Lighthouse is doable if you beeline it (and Suleiman is not in the game
).
I don't know about the others in the bottom part as I never attempted them, Colossus is doable but beelining Iron Working is off most tech paths (Education, Chivalry or Machinery).
The medieval wonders are 50-50, you can get them if you beeline them, but Alhambra and Chichen Itza are particularly hard.
Renaissance and later era you can easily get them if you beeline for them, but if you're late to the party you will miss out on them (so if anyone founds WC before you have Printing Press you will most likely lose LToP).