Humans and non-humans have been differentiated by their ability scores since the beginning of D&D. Non-humans are supposed to excel at one or two particular ability scores, and in older D&D editions non-humans often had penalties in one score (halflings were weak, elves had penalties on constitution and dwarves and half-orcs had low charisma). Humans were average, but they didn’t suck.
Surprisingly, in the current system, non-humans are effectively the same as humans in their primary scores (due to ability modifiers only increasing on even scores and standard array or 27-point buy). When compared to human variants, the human variants are now the ones with weak traits.
Sameness between races is further compounded by Ability Scores Increases as characters level up eventually red-lining several ability scores at 20 ( ie no differentiation)
It is interesting that when ability scores are listed for non-human races in the Monster Manual (or Volo’s) the ability scores tend to be double what player characters would receive (differentiation is preserved in those texts)
Here's my tuppenceworth.....Probably worth as much too...
Firstly, More power to you - the Rules are stated as being just a guide, and so adjusting them to your preference is using the rulebook to it's maximum. Bonus points for already implementing then too. Seems like your group is enjoying them as well....tripleplus good!
Secondly, for clarity I'd tweak your language in the original post a bit. There are two types of "sameness" at play when talking about stats: Diversity and Aptitude. Your homebrew rules focus only on the sameness of Aptitude. Now that's not a good or bad thing, but realise it does mean you are favouring one over the other (aptitude and diversity and generally at either ends of the same continuum). I'd put that front and centre, because otherwise people are going to argue cross points, which isn't helpful to you. You are buffing Racial Aptitude which is going to impact class diversity - accept that that is the starting point of the conversation and isn't up for discussion.
Thirdly, your rules as stated are sort of a double shot of Aptitude: Increased maximum and increased starting boost. Personally, I think it's a little too much especially in the world of bounded accuracy and only a exacerbates the bounded accuracy modifier variance between physical and caster stats (Unless you're an aasimar CHA based caster) - That is with standard array currently both your casting stat and phys attack stat have a max of +3 modifier at level 1. With your mods, there are lots of +4 STR and DEX options, but only 1 choice for +4 CHA and WIS, and none for +4 INT. This is just a balancing issue that, for me, jives a bit with the intention of bounded accuracy.
Fourthly, your ASI progression system means that for the bulk of classes, they'll only reach their cap if they spend their ASI increases on 1 stat. e.g. A goliath Barbarian can start with 19 STR and has 5 ASIs - all must go on STR to hit the cap of 24. While this isn't a problem for mono-stat classes, anything that needs 2 primary stats (Other than CON) isn't going to be balanced. Similarly, Humans now REALLY suck and have to micromanage their point buy progress.
Fifthly, it is slightly anti-scientific (HAHAHA - D&D scientific....oh I slay myself!). Basically, practice outweighs "natural talent" over time - Natural accumen gives only the initial boost, and direction of travel ("Hey I'm good at this!"), but it is quickly dwarfed by practice and training. I'll out benchpress a naturally strong guy if I do 10000 practicing benchpressing. If you consider level 1 to be a reflection of training up to the start of the hero's journey, this means years of training can never close the gap on Racial benefits. I know that's built in the current system, but your +4 and a maximum of +5 from ASIs compounds this even more. Petty i know, but I'm a science nazi....
Lastly, As a design decision, you are punishing non-optimization. Again this isn't inherently a bad thing, but it's there. Race becomes more of a decision than class, and you're locked into that specialization for longer (because of the ASI nerf). You are also incentivising specialisation over versatility - the 13,13,13,13,13,13 array can work brilliantly currently with various skills and feats (at worst you're taking a -1 hit from your primary stat at level 1). Under your system that choice is now void.
Personally, I don't like this because it hampers me as a player. I lean much more towards Diversity than aptitude (I like to deliberately try suboptimal builds because I
want to play the Dragonborn wizard who's jealous of his sorceror friends who don't have to study like mad to cast spells effectively), but that's how I want to play. It may not be how you and your friends enjoy your game, and that's cool (there's no badwrongfunning here).
In which case, I'd say you'll get far more mileage out of playtesting than asking people for their opinions because we're all playing different games. Objectively, there's loads here that throw the game balance out of whack
for the majority of games. You game isn't the majority, it's unique, and therefore the only balance is how much fun you're having.
Good luck!