At the time these rules came into being, they weren't about causing division, they were a result of division. Wealth and social status determined what you ate and how you ate it. The wealthier classes had more food, greater variety of food, more time to treat eating as a social event, and so rules arose around eating in company and eating for pleasure only, luxuries which simply weren't enjoyed by the labouring classes. When eating is for sustenance, how you hold your implement is governed by how easy it makes it to transfer the much needed food into your mouth. When eating is as much about socialising as it is about getting something inside you, in fact more so, you are going to be thinking about your appearance at the table more than the rumbling in your stomach.
The food was different too. Richer food not made to be eaten in quantity or at speed.
Later, yes, to a degree you are right, but it was less about exclusion than it was about the desire for the emerging middle class to be included. They didn't understand all the rules or why they were there, or even if they actually WERE practiced by the upper classes, because most had never eaten with someone of a higher class, but they picked up etiquette books and indulged in what was offensively termed by some as 'aping your betters'. As social mobility became increasingly a thing, this spread down to working classes, which is why so many of us with humble backgrounds learned all this from our parents, who got it from their parents, who got it from their parents.
Of course, it didn't bridge the social divide, but people thought it did. People thought doing as the aristocracy did gave them somehow more equality. 'I might not have what you have on the table, but I can hold my knife and fork like you, so you aren't better than me'.
And, of course, not unlike today, industry leapt on this development and sold the masses etiquette books and cheap versions of the crockery and cutlery the lower classes were led to believe the upper-classes used.
The aristocracy weren't interested in how we ate or what we ate from, because they knew perfectly well we wouldn't be eating next to them any time soon. They didn't use etiquette to oppress the masses and keep up the social divide because they didn't need to. The middle classes DID use it in that way, because they weren't secure in their position and wanted to slap down aspiring lower middle/working classes. But all this was a bunfight at the lower end of the scale. Meanwhile, the originators of the rules invented by themselves for themselves as fitting for their lifestyles were merely amused to see the rest of us desperately trying to arrive by imitation what they had by birth.
We're still doing it, and the real old money with titles and all that couldn't care less because they aren't at the same restaurants most of us frequent, they aren't inviting us to join them at their dining table and we aren't asking them to join us. I doubt many of us here know many bona fide aristocracy. Some of us attend formal dinners in the military, etc, but most of us, if we go out for meals are more likely to be eating at the local Italian, or pub that does food, or Indian, or Chinese, not a Michelin starred fine dining experience where people might notice how you eat your bread roll.
So for most of us, mouths closed, using a knife and fork nicely, and leaving them neatly on the plate to signify a finished meal will do. Waiting for all to be served is polite, so you are all eating together. Offering to others before serving yourself and all that, yes, ditto.
We don't need to do what Lord and Lady so and so did in 1845. We aren't living as they lived or eating what they ate. We do need to do what reduces mess on our clothes, doesn't result in our neighbour having to see (or wear) our half chewed food, and isn't going to make more work for the waiters.