I'm surprised they didn't go back to the lighting from unity. Consoles have enough power now to easily use it but I guess being cross gen has held this back just like black flag was.
The next one should be amazing graphically, not saying this one looks terrible but it could be better
Unity was not only the first one running on the then new and still current Anvilnext2.0 Engine, but was way too ambitious in the end for the hardware they got to work with, the given development time and the goals that needed to be acchieved. It got patched in terms of stability, gameplay, bugfixes, etc. and is now an enjoyable entry but since that they toned down the ambitions in graphical fidelity, lighting tech, all that for the sake of a more streamlined, smoother experience which seems to be easier to handle, after the following syndicate they either way switched up the formula but stayed with the same engine.
The next gen only entry will very likely run on a new engine (AnvilNext3.0?) and deliver a similar but ever so different experience, maybe tailored a bit more for the aproach the games take in the meantime. The first entries on the last engine were in one dense and vertical city, animation based combat games with small hints of something reminiscent of a leveling system and an economy, whilst after that the formula went towards rpg leveling in character and gear with loot, hitboxbased combat in vast open worlds containing multiple "smaller" cities.
The earlier games were built on Engines (maybe with the exception of AC1 which was on the same as Prince of persia) which were designed with a certain style of game in mind. The Ezio games had a clear focus on vertical city focused gameplay and an own Engine - Anvil. The Kenway Saga was about smaller cities, larger wild and natural areas and the sea (plus naval combat) and had an own Engine - Anvil Next and then after two City based games the whole thing crashed a bit with the unity launch and the lukewarm reception of syndicate they switched up the formula and pumped out three more games in the current AnvilNext2.0 Engine.
We´ll have to see how it will go, if they will take another risk with very high ambition or "just play it safe" and deliver upgrades but nothing that will make you say "yeah that looks like next gen" like the initial receptions of unity. until it launched.