The concept of an Arrowverse television universe and the reward it offers fans with its ideas is more than enough to overshadow its flaws, but the flaws cannot be ignored and will eventually become apparent either way.
The begining of everything
All universes have to start somewhere. For the Arrowverse, that started, obviously, with the Arrow series. No one would have thought that a universe could emerge from a single series, but some things about that don’t add up.
Essentially what the Arrowverse is trying to say is that there were no heroes before Arrow. Basically, he implied that without Oliver Queen (Stephen Amell) he would never have started other shows like The Flash with Grant Gustin or Supergirl with Melissa Benoist.
The Flash VS Legends of Tomorrow
Without a doubt, time travel is a confusing adventure in the stories of a superhero. Time travel is mind-boggling and can be difficult to figure out. But what makes it more confusing? When there are two different types.
Both Flash and Legends Of Tomorrow are concerned with traveling through time and messing with key historical events. The strange thing is that when Legends, a team with some members as powerful as Flash seem to be better.
They mess with time and can somehow easily fix it, whereas if Barry Allen (Grant Gustin) goes wrong with one little thing, he creates a whole new reality.
Freeland and National City
Bringing National City from the world of Supergirl and the world of Freeland from Black Lightning to the new Prime-Earth does not add to their series, especially with the end of the two shows.
All it does is add to the world-building aspect that it will end up being obsolete, this because no future use has been known for these venues when their respective shows end in the Arrowverse.