One of the coolest games I've ever played.
The topics explored in the main story deal with security at cost of liberty, the power of misinformation, the potential of technology's possibilities, and other neat stuff that have you question the path modern society is currently on.
Gameplay wise Watch Dogs Legion allows you to play as anyone you can think of who would live in a city like London. Some characters are more distinguished than others in regards to what they can offer your team, but everyone can be apart of it no matter how useless they may seem. Different characters have different abilities that force you to approach missions in different ways. A spy may choose to sneak past enemies to reach their target and download what they need for the objective while a hacker may navigate the areas camera systems to get close enough to the target without ever entering the area. And then a construction may use his cargo drone and just fly over everything to the target. You have options but some are more effective than others depending on who you're playing as, and this creates interesting scenarios that you need to navigate with your available resources.
London is gorgeous. Dozens possibly over a hundred of unique locations make up the city for you explore. There are plenty of side actives in the world from organized fights to playing keep-it-up with a football to grabbing a drink at one of the many many pubs.
Point is the games fun and you should play it if you want a new open world to explore or are interested in near future sci fi concepts