Curb your gatekeeping. There's nothing wrong with looking at what the competition is doing, and borrowing/becoming inspired by them (see the entirety of the Forza franchise and its popularity). It's honestly required to a certain degree to stay relevant nowadays.
I do play Forza (playing Horizon 5 right now as a matter of fact). The Forza series is the reason why I want PD to add these aspects, because the series (both Motorsport and Horizon) has taken what made GT series great, and has expanded on those ideas over the years. Meanwhile Kaz still makes his games thinking that GT still sits in its own little bubble like it used to in the 2000s. I have a feeling that I'm not the only one, because you don't have to look very far to see people going for the "flash" with their cars in GT7, or see people making Need For Speed or street-racing style videos in the game, either.
If Kaz well and truly wants GT to represent car culture, and for the series unquestionably occupy the top spot like it used to, than he has to pay attention to what their competitors are doing, as well as what's popular in the car world currently. No ifs, ands or buts about it.
BTW, this is coming from someone who has grown up with GT since GT3, and has all the games up until GT Sport, including a the Japanese of GT1-3, and 4 Prologue.
Indeed, but that's only one facet. It and the performance customization options in GT7 are both major steps up from previous GT games, but as a package what's present still lags behind GT's competitors.
Do you know this for a fact? Are you minutely aware of how PD handles their workflow and what they assign to their employees?
I don't disagree that GT7 has a lot more pressing concerns, but there's nothing at all wrong with asking why there aren't more options for tuning and just general things to do, because things like that help extend the longevity of the game.