I've flown extensively with UA, LH, TK, DL, AF, and KLM - in my experience, TK customer service as been the absolute WORST in this regard. The other airlines can be quite abysmal in other aspects, but regarding customer service on the ground, oh man - TK is simply a nightmare. Too many horror stories.
Regarding your point - it is known that some *A carriers (LH group and others) do not give free checked bags in basic economy, even for elite passengers. It's the same with BA, or so I've heard.
Yeah I found out after I saw my ticket but when I chatted with UA and saw their bag allowance, I thought MSC applies in the US and Canada and apparently they do not. I actually took a screenshot to prove that UA has provided me wrong information. They should really list this properly before I press pay. I think this is only LHUA JV and SK and if I check in an UA flight I would get a checked bag, but not with LH group. Absolutely pathetic - totally . At least TK gives 2 checked bags for North America route.
Check out the LH/KL forum on how their customer services deny their EU 261.
I have received terrible ground service from Eurowings, Eygpt Air and SAS. I don't fly ST so I have no idea how they handle things now but about 15 years ago AF broke my stroller and they demanded me to get it fixed in a shop 50km each way from my home. A friend of mine was really upset about DL/AF/KLM lost her bags and couldn't fine it. It took me 2 hours waiting time to get to talk to someone at OZ to try to book an award ticket with *A. I couldn't even get through to BA's customer service. I haven't bought tickets with LH for a long time as their K, L class earn nothing for TK M&S.
That's why I said customer service is something that's declining - look at amazon.
The 15 minute schedule change is pretty special with TK. UA has 30 minutes schedule change policy but only within 150 miles destination change. I can imagine that it's something more for the CSR to learn. I look at buying flight ticket like a package - TK has no "basic economy" BS which I really like, and the fact that their Y product is still way ahead of LH and upgrading Elite instead of looking at booking class. I know their customer service is not top notch but it's a small part of the price to pay for the rest of the benefits.