I think that when you have 6 numbered installments that seem rooted in a Career Mode with ever-growing features, it becomes pretty difficult to communicate a shift like Sport.
I mean, right off the bat, using the title "Sport" instead of a number seems like a pretty obvious symbolic choice, and revealing the game with an outline on a persistent multiplayer experience did draw some negative backlash.
However, as a long-standing GT fan, I feel like this is the most polished and interesting effort for the series in a long time, even if it lacks some features that its peers have pursued in recent years (dynamic day/night and weather).
Every activity in this game -- whether single- or multiplayer -- now centers around a single persistent driver profile that is socially shared (via the online network), but the breadth of activities that existed in other GT games is still largely present, it's just not accounted for in the same "Career" structure that's been familiar to fans for a long time. Where this gets even more hazy is in small places like how your DR/SR -- two of the most important aspects of your driver profile -- aren't affected by your single player activity, which makes the lack of a Career structure stand out a bit since it still shows some discrimination in priority over what activities the game deems more important than others, running counter to this universal/social notion it seems to be built on.
We also had to take a hit on the content levels for vehicle count and track count, as this game was built from the ground up for PS4 tech in response to the infamous use of PS2 assets in the previous PS3 installments. While it is a pretty drastic reduction compared to those games, I think that the high level of detail and individual attention paid to the way cars behave at the lower car count has proved to be its benefit, owing to more distinctive car properties and a more robust range of engine noises.
And this is just a personal take, certainly not one I think will apply to or interest all long-running GT fans, but the multiplayer genuinely addresses most of the aspects of online multiplayer racing that intimidated me before, and now it's enjoyable, an entirely new approach to "casual sims" that I never really ever paid any attention to before. It doesn't make me immune to making embarrassing mistakes, and it doesn't necessarily make it so that I can completely avoid bad driving practices and poor sportsmanship online, but the safeguards in place literally feel like every effort to play fair-but-competitively is honored and rewarded at most times -- a remarkable majority of the time, even. I'm actually glad that these considerations seem to have been the focus of the development of Sport after all, because it's actually making me interact with GT in a way I always felt too intimidated to as a casual player, and making GT feel perhaps far more fresh and exciting than just getting yet another predictably structured career mode has.
On top of that, I think they absolutely nailed various aspects of presentation that they aimed for and fell short of in the past. Menus look and sound beautiful and seem to contextualize Gran Turismo into a larger, more human experience, rather than a museum-like ode to car and motorsport culture only. "Driving is for everyone" feels like a well-achieved mantra for this game, despite some of its shortcomings in respect to long-running expectations whenever a game is titled "Gran Turismo" and a number is placed behind it, or when compared to its peers on market. It's still a unique, polished, and well-designed "casual sim" experience from the ground up, even despite many of the criticisms that can reasonably be held against it for carrying the weight of "Gran Turismo" title. I'm not saying that it should have been called something else, but I think putting "Sport" behind it was all the indication you need that they were trying something different -- and I think, even as someone who adores the long-running numbered titles in the series, they absolutely pulled off something special and worthy of their time and effort here.