Making a homebrew race with a natural ac, and trying to balance it.

I'm currently working on a homebrew dhampir race that has a natural ac, and doing my best to try to balance it. I'm wondering if it's too unreasonable to even try to make any homebrew race with a natural ac, I know for the races that get it, it's typically just one stat plus 13, and allowing for shields, so my alternative formula has been 10 or 12 (leaning towards 10) + dex + other stat but no armor or shields. I just got my homebrew race shot down for a one shot because it was considered too overpowered for a race to have a natural ac built like that, I did the math and 10 + average dex and other stat would equal to about 16-18 and being limited on increasing that ac with set add-ons (through items that require attunement) makes up for other option of ac with armor and shields (that can get enhanced and do not require attunement). The average armor ac is 14-18 with a bonus of shield, most get access to higher tier non magically enhanced armor in the early game (progression between levels 1- 8 ish), while the formula I made at typical best would start with 6 or 7 + 10 for starting ac (at most without inflated stats, especially with point buy or standard array), and it evens out with the general 16-17 starting ac of most natural defenses, or shield and or armor bonuses. Additionally there are 4 main ways to increase ac using the formula I created and I would argue it is balanced out with taking up an attunement slot, while using armor and or shields does not and those can get stronger, while the attuned items do not. Stat increases both boost both formulas (though at max without magic items, my formula maxes out at 20, while with armor and general shields (at the point where 2 stats are maxed out, would typically have access to magical armor and or shields (unless inflated stats to start), being around 20+. The only way my formula could be easily overpowering in terms of higher ac progression than other formulas is if you start out with like 2 18's before asi from races, which would either means; everyone else has 2 18's or something similar or your 18's get nerfed, depending on how well you rolled the rest of your stats and how well everyone else rolled. I could maybe see you getting a possible advantage with that, but it would be equal to most natural defense sources, or if you can start with better armor in that situation with 2 18 stats. If you start with 2 18's with racial bonus, it would still be an ac of 18 and take you until level 8 to max out if you took 2 asi sets, and by that point most people would be around 18 or 20 ac too, or higher if using magical shields and stuff. I am mainly comparing my formula to that of like lizard folk or something similar due to them both being applicable to classes with any kind of armor or shield proficiencies, if any. max dex + 13 + shield is 20 plus a non magical shield, can be achieved at a sooner potential than 2 maxed out stats, no magical item. By the time my formula can get something like bracers of defense or something similar, others could get a better shield or magic items to also boost ac. This is my thought process and logic behind why I think it would be okay, but I also want to hear other people's opinions on it. This formula would be used on a race like a dinosaur or some maybe mythical race or something like that. Stuff I have tried to balance this formula with is something like, limited healing options, or a vulnerability or some kind of drawback that helps balance it. Any and all respectful criticism and opinions are welcomed, and main point is to see what people think and have a respectful discussion like thread going about this kind of homebrew racial trait or I guess class feature too, and if it could be balanced within many different campaign settings.