Of the 427 cars that GT7 launched with, 168 had been in GT Sport on day one - some much earlier than that in the GT Sport Beta. Players have therefore had four years and nine months (well, less a week, or add on seven months for the Beta cars) to race, tune, experience, and learn the history of these vehicles.
From those 168 cars, the history of 66 of them was "we just made it up for the game" - as variants of existing VGT cars (the history of the LM55 is definitely something you can learn, the history of the LM55 Gr.1 is the exact same thing - it just has "Gr.1" on the name now), or fictional Gr.4, Gr.3, Gr.B, and Gr.3/B Road Cars.
Over the four years and four months and three weeks, PD added a further 169 cars to the game, at an average rate of 3.2 cars per month. That allows players an average of over a week to race, tune, experience, and learn the history of each car. However the last of these cars came in July 2021.
GT7 launched with an additional 90 cars and has since gained another six. 39 of these cars are from previous GT games, and seven are "we just made it up for the game" variants of existing VGT cars, fictional Gr.4/Gr.3 cars, and one badge clone whose history is tied up in that of another car in the game.
That means that anyone who has played through the GT series has had 44 new cars to race, tune, experience, and learn the history of, over the past four months and four days - or around 2.8 entire days with each car.
Anyone who thinks it's impossible to have experienced every car GT7 has to offer - while simultaneously decrying people who want to have every available engine swap in order to experience the 25 additional vehicles - is so delusional they probably still think homosexual slurs are appropriate behaviour in 2022.
Edit: Oh well. No value lost there.