Always flying out of EZE, this post caught my eye.
Just a few comments from my end, as a regular user:
At Check-In, AA/EZE normally has 2 initial "status check" podiums (Priority and Main) before getting to the counters. If you approach the Priority podium (furthest to the left when you get into the airport), they will normally ask for your flight number and name, check on a printed list and show you to one of 2 lines: Platinum/Platinum Pro/Business to the right and Concierge Key/Executive Platinum/First Class to the left. These lines will take you to the check-in counters. There are normally 2 dedicated counters for CK/EXP/FC, and 4 for PLT/PPR/BIZ, although depending on the time of the day not all of them may be manned.
There is no dedicated/separated area for Flagship First Check In (as you can see in MIA/LAX/JFK/LHR/ORD). And this is the only (out of 4~5 daily AA flights) with Flaship First Service, which has been running on and off for the last 12~18 months.
Still lines are not very long and staff is quite good at processing passengers, so it shouldn't take long to get through this.
About the lounge, you are absolutely right. Over the last year or so it has become more and more populated, to the point where people end up going to Latam or Amex lounge. Both AA and IB share the lounge and have flights departing within a 3-hour period, which brings a lot of people into such small quarters. LATAM tends to be quieter and offer better sitting options, but it also depends on the time of the evening.
As for the service, with anything AA, it's a matter of luck (shouldn't be, we all want -and pay- for a consistent and excellent service, but you get what you get..). I've had some great crew on these flights (EZE/US) and some crancky folks that shouldn't be in front of a customer. Most of the times BUE-based crew are professional on how they carry around the flight but I've noticed pursers and FC FA to be "juniors" many times.
Regardless, they should check catering and beverages, and should be aware if all is set for their "shift", yet doesn't always happen like that. Most of the times they board the plane 10~15 mins before passengers and they are expecting to show up on the basis all is set and done accordingly for them to do their job.
Finally, personal appearance is quite controversial to discuss. I do share your opinion that many other airlineshave their crew really polished and looking sharp, but with AA is a very mixed bag, with probably "light" guidelines that leave too much room for personal interpretation. And this wil happen with any AA crew.. wherever they are based..
A bit off topic, but on one of my MIA/EZE flights last year they welcomed some new AA crew members. One of the ladies was working BIZ and I could hear when some senior FA said "relax.. you're not at EK anymore.. you don't need to be.. so.. 'dedicated'..".
Aside of this experience, I hope our OP had a great time in Argentina and will return soon.