Walaikkum assalam wa rahmatullahi wa barakatuhu,
Some of my opinions. I might be wrong but this is how I see it, from my experiences or reading. There is nothing wrong in Islam by seeing family, culture, or beauty. It is correct that the criteria is piety. But, that is what is deciding criteria. For. e.g. you could have your requirement as same culture, language, beauty. When everything that I mentioned before is satisfied and then you check piety, if it is a pious woman or man, then go ahead, if not, look for someone else. That is how it is in Islam as I understand it i.e. they final deciding criteria is piety. So, there is nothing wrong in having conditions like wealth, family, culture or language.
And I do not know how online matchmaking or hired matchmaking works. In my knowledge of how it works in my family, we do not contact any professional match maker or anything. Because, it is all about trustworthiness and accountability. If the marriage ruins, then you cannot go and grab the collar of the matchmaker. In my family, usually it is based on trusted chains, for e.g. we need recommendations from family.. i.e. some one far related might know of a good, pious family with a man or woman who is looking for marriage. This is through spoken word. Sometimes, even recommendations from people in Masjid whom one is friends with. So, parents trust when it comes through people who they know and are in good terms for long time. And it is perfectly understandable. They do not do it because they are xenophobic or hate other cultures. It is basically fear of the unknown. How can they take your word for it? They want their children's marriage to be good and a success and they want them to lead a good life. They fear if they do something that they don't understand or have complete knowledge of, it might ruin the marriage. But, if they have the word or recommendation of someone from family that they trust, they can expect some kind of assistance in times of trouble. I, mean, in the subcontinent, kinship is something that everyone values and I know islam places much importance on preserving kinship. Also, marriage is more than just for two people involved. Firstly, it is for Allah. Then, parents either want to make stronger ties with their own near families or include a new family into their domain, thereby expanding it. So, that is why they go through trusted means so that the new family that comes in is pious and in good terms with rest of the family.
According to me, an online venture or hunt for spouse or hiring a matchmaker is not the usual medium. I am not saying it is not the good medium or way. But, we tend to stick with what is usual and working. So, in my opinion, if you have to be a successful and efficient matchmaker, it can be only in a domain or region of your influence. So, you should probably make good friends with other muslim mothers in your area and probably, after they are confident about you, they will ask you for someone for their daughter or boy. The problem is those who want to get married come to you directly and not through their parents. So, it is easy to convince people who want to get married through their parents than to convince parents through their children. Just my two cents. This might not be the case everywhere. Forgive me if I said anything wrong because of my immaturity and ignorance.