Its an image thing. A kohen during the times of the beis hamikdash had to have a certain look to him. He had to have certain clothes, he couldn’t be too ugly or aesthetically unappealing by missing an an arm for instance, he also had to have a certain wife. Its a tzurah- a look.
If there is no halachic issue and you want to marry a ger or giyores dont worry about it, you dont need to have that image today its all good. Thats my take.
Im just curious, would you not have married Ruth for your rationale? Then we would not have Dovid Hamelech.