To begin with, traction control and stability control are an outright disadvantage in the vast majority of cars to any experienced player. Exceptions include the C 600 powerbuild Reliant Supervan, used for cross country and dirt events, where TCS enables more precise control over bumps. There is no known situation in the competitive community where STM is faster. When considering the pace difference of meta cars, it is important to remember that in order to extract said pace, a driver must have the skill to do so. Examine the laptimes on Horizon Mexico Circuit, for example; a track where powerbuilds hold sway in every class by a comfortable margin. Since you mentioned the Bone Shaker, let’s look at the A 800 leaderboard. The world record stands at a 59.787 in the 1932 Ford Coupe, with the Bone Shaker having achieved low 1:00.xxx on several occasions. However, these vehicles are both powerbuilds, and are seldom used online by casual players. The most popular build of the Bone Shaker, which is AWD and the one you are most likely to encounter online, is capable of 1:01.xxx. For reference, what is considered a ‘good’ time in a balanced/AWD tune for this track in rivals testing is somewhere around the 1:03 mark. Now, we consider external factors. Two seconds per lap may sound like a lot, and in a competitive environment it is, but in Horizon Open, considering the frankly colossal skill discrepancy between players, most will struggle to drive below a 1:07 in the Bone Shaker even in optimal conditions with no traffic. The equivalent to using autoaim in a shooting game would be using autosteer - and even that wouldn’t be fast. AWD meta cars are only as good as their driver. The same applies even more to powerbuilds; in order to succeed in them, you need to have good throttle control - TCS doesn’t replace that. TCS allows you, once you have set off, not to spin the wheels on corner exit. It does not replace the terminal understeer you would experience with a normal driving style (slip angle is necessary to keep most powerbuilds in A class and below from understeering at speed), or the wheelspin experienced at the start of an event. Most users of powerbuilds will be reasonably skilled, as it takes practice just to keep the car going where you want it to. At the end of the day, most people who use meta fall into one of four categories: people who want to win by any means possible (including but not exclusive to rammers, cheaters, headhunters, etc); people who want to participate in the battles at the head of a lobby but lack the pace to do so in a non-meta car (usually reasonable but not excellent drivers who want to improve their racecraft/skill); people who are attempting to become more skilled with a specific car in a racing environment for any number of reasons (e.g. personal satisfaction, rivals runs, internal championships, time trials); and those who are simply testing and refining a tune in an online setting. Personally, as long as someone races well, I couldn’t care less what car they’re using. While I avoid meta myself, I’ve had some of my best races with people who are using meta.
TLDR: Horizon Open isn’t just about you. People have their reasons for using whichever car they want to, and you have no right to stop them. Sure, it might annoy you that you’re losing to them on some occasions, but if losing bothers you so much, either use a meta car yourself, find a different lobby, or find some way of improving. If people want to use meta, let them; it’s not a felony. There are much bigger problems in the online community such as rammers, cheaters, autofinishers, etc which have a much larger impact on racing than someone who is using a fast but completely legitimate car.