Way too many Americans learn their grammar from various media, not from English teachers.

Y'know, when it comes down to it, the grammar is only important ... never.
The important interactions happen in real time, face to face.

We exist with a sense of understanding that is pale in the written word.
To communicate effectively in person is much, much easier than in the written language.
This is why it is so important to actually meet the people you might enter into a relationship with.

Sure, the grammar helps with the vetting process but some leeway must be given in favor of finding the 'target'.
Just because a person hasn't the ability to be fluent in written correspondence doesn't mean they are not fully able to carry out a meaningful conversation in person.

Placing too much emphasis on written grammar cheats potential mates and limits your match pool.

Personal example: The woman I am currently seeing had very little ability to express herself in the written word but in talking with her and NOT JUDGING HARSHLY, I found that she expresses herself very well verbally.

If you are writing stereo instructions or law, yes, what you write is important. But, when you are looking for someone to spend time with, the expression that matters is the actual 'one on one' expression that has very little literature involved.

Of course there are exceptions to the rule, there always are, but leaving those out of the equation, I don't agree with you.
People who cannot write properly usually aren't too bright either. People who are bright typically also want to learn, meaning read. They also want to learn specific things about specific subjects that typically don't interest the other group so much.
And without wanting to be judgemental, I do believe many of those not so educated/bright people often come from a specific background/type of family. Just like the more educated and brighter ones do as well. Typically ALL their siblings and parents are well educated and have good jobs too.
Getting proper education isn't dependent on income of parents. Over here everyone has to go to school until they're 17 and 7 months old, and EVERYONE has a chance at getting to higher education. It's up to the kid and their capacity. For the cost involved for secondary school (books mostly) you can get a subsidy that covers most of it.
If you want to continue studying after that, you can also get a subsidy, although I believe these days it's often a loan.
In any case, basic education is available -and mandatory by law- for everyone.
The ones who don't pick up on it, or stick to the lower levels -which is a huge group- mostly come from a specific background. I'm not making that up, I've been a teacher for a number of years. You see few kids from 'better situated' families at the low levels.
Some who are at lower level are children from refugees because they don't master our language so well yet. Crying shame, I have seen some bright non-Dutch kids, but you know, the ones who are bright WORK. They LEARN. Because an eager mind is wired like that. And they work their way up and still go home at the end of the day with a good diploma AND knowledge and so on. Because they DO have the capacity.
There simply is a group that doesn't have that capacity so much, and that group is large. I think at least 50% of population, I suspect more. (Just thinking of my teaching days, secondary schools have 4-5 different levels for the not-so bright ones, only 2 for the higher education levels).

Of course these days there are also quite a lot of dyslexic people, increasing amount I think. My son is mildly dyslexic too. Never liked reading because of that, easily got overloaded by the typical school textbooks too. High Sensitive New Age child, like so many these days.
BUT... he still got a manager's diploma at a higher level, without much effort even. Skipped school so much authorities stepped in a few times (I didn't know, grrr). But he made it nonetheless. Now he is highly educated, and also partially self-educated on many other subjects. He doesn't read like I do as he's dyslexic, but he finds out via the internet, mostly videos.
The chit he knows on quantum physics, insight in life & psychology & people, and so on. It started with investigating Illuminati, free mason, and whatnot, as a teenager. And he KEEPS learning as he has that mindset. I'm almost way over my head when talking to him, haha.
Gave him some figurine copies of the Terracotta Army for Christmas, well prepared to tell him what it was about. No need. He already knew. Even knew the name of the emperor who ordered them made. I was flabbergabbered, lol.

All this stuff is exactly what many people who cannot write properly do not have. Somehow their brains are wired differently I think. And it's not just the writing itself that gives that away, it's also the things they talk about and/or are able to understand.
As for your woman... my son is also with a girl who isn't all that educated/bright. It's a sweet girl, but I never understand how he can live with her. He cannot talk about any of the things that truly interest him because she's mostly interested in fashion shows and make-up and expensive clothes.

Comma splices are evil.

basic or dumb phones like the razor or star tac, only had a number pad with letters attached like on your house phone. so typing words required either multi taps to get the correct letter or one touch for each letter and letting the database show you matching word possibilities (t9word)

Oh, heck yes! I remember now, haha. My very first phone was like that. I just checked. Yes, I still have that baby, over here we call such large/old phones "a fridge", haha. I've intended to dump it for ages, but need to dispose of the battery separately and it just never happened.
It's been living on my microwave for some 5 years now, waiting for disposal. Before it was in a drawer for years, decades? So it IS getting closer to the bin, haha.
Thanks, for reminding, I honestly couldn't remember what else we'd had. Go figure how easily you adept, and forget.