For me, GTS and GT7 are way better than FM7, and I think the FM devs understand this which is why their new game has taken so long.
I saw FH4 as a better competitor to GTS than FM7, having great fictitious tracks like GT does, better driving physics than FM7, and a proper multiplayer rating system. However, it also had things I found frustrating, which is why I eventually stopped playing it, such as the failure to fully address ramming in multiplayer racing, bad workflow in some areas such as rivals, the weekly chore list which I absolutely hated. The races are also very short, and lacking in any strategy as there's no fuel use or pitstops to change tyres etc, so if multiplayer racing of that nature appeals to someone, it doesn't come close to GTS/7.
GT7 has brought it's own frustrations, in particular the fact that it's very focused on car collecting and has very few races that give the best payout per minute. It doesn't have much in the way of time trial leaderboards, so there's ultimately just not that much to do in the game, which made me question why I was even collecting the cars anyway, when there's not much to use them for once you have them. If you're into PvP racing with strategic elements it's probably still the best of the most well known console titles for that.
I've personally mainly been playing The Crew 2 for the last month, as I feel its competitive weekly summit events are better for time trialling than anything GT or Forza have to offer. It also has its own frustrations, though, e.g. it's mind blowing that over 4 years after release it still has no way to scrap all parts in the mailbox. If I had paid full price for it at launch rather than buying it extremely cheaply in the Steam sale, that sort of thing would undoubtedly have me absolutely raging by now.