I don't mean to be an intentional devil's advocate for the sake of argument, but the guardrails have been the opposite of what you say, being a devastating issue. Whilst you assume they are irritatingly penalising, Japanese speedrunners have used guardrails to their advantage to get times of 1:30s, since at certain angles they don't affect the car (they are getting mega-nerfed). Overall, gt2000 is fine as is cuz it was added as an inside deal between someone in the discord and MoiDev, not intentionally meant to keep up.
TL;DR guardrails don't really penalise, were used in speedrunning. GT2000 is garbo intentionally.