As strongly as I'm in favour of keeping racial ability score modifiers, I'm just as strongly against ability score penalties, and even more strongly against the idea of different races having different maximums. It goes against the entire philosophy of the design.
In particular, the caps: Olympic athletes in our world are not 20s. They are 17-18 at best. The cap scores, are individuals whose ability in those areas is super-mortal, and level 20 characters, who might have several scores at 20, are themselves on the cusp of demi-god status. This is a point where, thematically, the differences between abilities based on their race are so far left behind as to be non-existent. If you have 2 level 20 wizards and one of them is a half-orc and one of them is a gnome - and they are both the peak of wizarding capability and breaching the edges of mortal capability... No, at that point, the gnome does not have an edge on the half-orc. Not any more.
The whole point of the system as it was developed is that while we are all different and have different strengths and weaknesses innately, as part of our heritage, anyone, from any walk of life and any origin, Can aspire to the absolute maximum of mortal capabilities, and, if they put that work in, can be just as good as anyone else who does the same. That was the point. From a mechanical point of view, it was also designed to ensure that no-one was actually penalised in their ultimate capabilities by the race they picked - there would be differences early on, but ultimately, they would not be any less capable than any other choice. Removing that would be a step backwards in system design.
