GT:Sport is primarily online focused. For that purpose yeah it's very good - pickup races basically work and theirs safety and driver ratings to match make against. If you just want to do some offline career style play, not so much.
As a single player experience - it's dry since the career mode mainly consists of doing challenges and events. In that sense it's not much different to previous GTs but the customizing of the cars is reduced. The racing AI is improved over what it was but still lacks a certain something. It's almost too robotic so there's not that feeling of competition, but if you're driving "properly" then the AI is at least more likely to react to you in a reasonable way. Drive erratically though and the AI gets confused and just sticks to it's line no matter what.
To be honest, I never thought of GT as a "career" simulator and the customizing was kind of unrealistic so I didn't like that side much. For it's time it was good but better stuff has come along.
GT Sport is great for the multiplayer stuff, it's pretty generous with cash to buy new cars and as usual the graphics are phenomenal. But, if you're into iRacing, then that is a better driving/racing experience (and probably rFactor, pCars and Assetto Corsa are too but I haven't tried those for a long time) - GT has some features borrowed from iRacing and that's where it's focused.
Photo mode is incredible too if you're into that.