In the specific sense there never was *a* paleodiet. If one looks at it anthropologically/archaelogically humans have subsisted on just about every diet imaginable, from an almost pure meat and fat diet, by way of fruits, veg and all the seafood you can imagine to predominantly vegetarian. I can't recall seeing purely vegetarian pre-agricultuee, but please add to my knowledge if you can.
What everyone (almost) is in agreement with is that we eat too much procesed food, probably in many cases too much carbohydrates (in general), sugars (in particular) and fats for our current lifestyle. Ecologically and from a climate perspective reducing red meat consumption might be a good idea (of course this depends a lot on what species and how it was processed, culled roe deer and factory farmed beef are not equivalent...). Fish? Generally seen as good for you, but look out for the levels of dioxin, mercury, PCBs, etc in many populations*. Talking about populations, we really should stop all commercial fishing for a decade or so, then our children have a better chance of ever eating fish from the oceans when they grow up.
So my suggestion is: eat a sensible diet (i.e. not the fish and chips diet, not the "half my calories come from soft-drinks" diet, not crazy fad of the week), and you should be fine. More real fibre (i.e. not the articificial "technically a fibre" stuff) is probably a good idea, mixed veg and not too much grains, keep an eye on the fats and sugars, and you will be in good shape.
* Sweden got an exemption from the safety levels specified by the EU, since else very little of the Baltic herring would be considered edible. I love my government, and it only wants what is best for me. They keep telling me that, so it must be true, because they say they would never lie to me or decieve me.
