A very good question, a call for experiences, and then a thread which seems to have deteriorated into Japan-slammig with some wildly inaccurate (perhaps biased) comments. Anecdotally everyone may have different experiences sure, but that does not a pattern make. JL is head and shoulders above most airlines on all aspects of its product. If check-in takes a long time, it may just be your day for a slow day. Most of the time it is fast and efficient. Perhaps the inability to respond described above goes to the typical structure of the silo-like structure of many organizations here? I rather guess it does. In a perfect world, everyone at a travel company would be bilingual or have access to someone in their immediate team who could take over communications if tit were in a ,language in which they were not proficient to the extent required by an irate customer. As a point of comparison, try checking in in Japanese at JFK, LAX or SFO with anyone but the simple Japanese duty manager. It simply is not possible. And that to me is a far more egregious error. I have never gad a long check-in time with JL or NH, but I do tend to check-in online, and I also speak Japanese at a native level of proficiency. Perhaps better communication has positively impacted my interactions?
So to answer the question initially posed, no, the service has not declined. In fact it shines even more brightly as an example of how to do things in the post-pandemic hyper-travel era.
Comment is strange as it makes many assumptions with bias while ignoring own bias. Poor experience was not language related as it was done in fluent Japanese as my companions were Japanese. Probably made it worse in hindsight as they treated English speakers at other desks better. I think it just comes down to new employees don’t get enough training, don’t know the actual rules, and when they are wrong cannot admit it or fix things.