As a pilot about to retire from airline flying, here is my point of view.
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No need to say, I have positioned numerous times as SLF myself, on my own airline and other air carriers, worldwide, and come to have opinions as well. Obviously, the typical 23 years old "Singapore Girls" or "Cathay Ladies" smiles have a tremendous commercial value to their respective airlines. And yes, it is true that US air carriers, nowadays have rather "senior" (by age) F/As.
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Male SLFs discriminate by gender, maybe. They do object to a 50 years old female F/A, but if the F/A is a male of 50, there is no criticism. What is being said about salaries and retirement pay, in particular for US air carriers is absolutely true. These days, their salaries are peanuts, and their retirement is close to zero, with almost no benefits.
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In the old days (I started airline flying with PanAm in 1969), F/As were highly educated and well qualified to be selected for a rather long training of very high standards. I remember many were with, say, nurse training, bilingual at least, if not multilingual if the airline operated overseas. They knew what the local time was at your destination, and that German is the language in Zurich. They were trained to serve first class meals and wines (in suitable glasses) and knew how to present cutlery and fine china to your seat. They knew what to suggest as cognac or whiskies.
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They were discriminated (yes) for their public appearance. Female F/As were not supposed to be married. There was a limit to their age of forced retirement (if females). Male F/A (then called "stewards") were generally on galley duty, while females (often called "hostesses") served in the cabin with a pleasant smile.
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Then, all that changed, in the the 1970s...
The FAA minimum F/A training became soon observed, if I recall, some airlines could train new F/As after a mere 2 weeks, of which 40 hrs of classroom training (with numerous coffee breaks) and a couple of flights for practice. Since English was the "aviation language", it became unnecessary for them to know anything but Brooklynese or Ebonics.
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Older (senior) flight attendants in the US are still the ones who will know best how to get you out of the plane in an emergency. They are on board
to save your ass, not to kiss it. I regret that US airlines have such a low standard of selection, but what do you expect to get with such salaries. It is the same for pilots... peanuts.
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As a pilot, I rather have senior F/As to work with. They know how to handle the passengers, and what to tell them. Some of the seniors even have a list of their pilots with the way they drink coffee, black, or with cream, one or two sugars... I hate to be babysitter when on layover, to tell them that the voltage at hotel is 220V, that you look to the right first to cross a street in Capetown, and that you need an ID to prove your age for a beer in a Chicago bar.
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The trend is about the same in Europe, than it is in the USA... although F/As there are often able to speak 2 or 3 languages (except if from UK, then it is often English only). As I live in South America, we still have above average cabin service. Often used to take the 50 minutes long flight "shuttle" from Rio to Sao Paulo, and these excellent F/As manage top class service (in Y class) with a full meal, a before dinner drink, a meal, coffee and after dinner drink and all that with a smile. This with Portuguese, or English, or Spanish as a minimum, some even in Japanese, Italian or German language.
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In the US and Europe, the public wanted to pay less, so they got LCC...
Now they have LCC level F/As...
US airlines, no thanks for me, except maybe Southwest Airlines, they are my choice when in the USA.
I do not care. I retire in November, and my little car is all I need to travel in Argentina, Brazil and Uruguay.
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Happy contrails