What change are you proposing, exactly?
With any competitive game wherein players have a variety of tools at their disposal, it's natural that players will gravitate towards the strongest and most competitive option that the game allows. It's the same with competitive Pokémon, where top players use the same 32 species in a game with over 800 monsters to choose from. In GTS and GT7, it's usually only one or two cars in a category of 30–ish that get to shine.
In an ideal situation, every car will have its unique set of strengths and weaknesses that allow every car to shine every once in a blue moon. I will admit that the Atenza's straight line speed is so ludicrous to the point where it far outweighs any cornering downside it has (and it corners like a bloated, drunk pig). It does tend to murder its front tyres over a long stint, which makes it almost drawback free in sprint races with low or no tyre degredation rates. Many have wanted to split Gr.4 into GT4 and TCR classes, and seeing this mess, I'm very inclined to agree.
From what we've seen in the 4+ years of GT Sport, BoP is a constant work in progress and is never perfected. I think Gr.3's BoP in Sport currently is in a really good place with only RWD cars, but Gr.4 and Gr.1 especially have been a disaster that PD just didn't seem too interested in balancing, with a mix of drivetrain layouts, number of forward gears, and driven wheels across literally decades of motorsport.
The flaws of the current BoP is plain for all to see, but I don't know what can be done to solve the problem aside from refining BoP through months and months of trail and error. Maybe Sophy can run all Gr.4 cars around all the tracks in game and average out the cars' performance...?