I was prompted to make this thread as a reaction to this one:
D&D 5E - Orcs and Drow in YOUR game (poll */comments +)
...in which the OP has created a poll with a variety of options, yet
none of them anticipate the possibility that people just wouldn't use alignment at all. Since my perception is that a significant minority of players/DMs in fact
don't use it at all, and a majority of players/DMs do use it but only "lightly", I was surprised by the assumption made by that poll that everyone uses Alignment as a matter of course. I was curious about whether my perception was wrong (it wasn't) but the purpose of this thread isn't to determine the one, true God or to convince others that there use/non-use of Alignment is wrong. (Of course, it's devolved into that - but I was more interested in taking the temperature for where Alignment use currently stands.)
I do think the one point you make above, that Alignment "always will be" part of D&D, is less set in stone than you think. Personally, I expect that in 2024 it will be relegated to an "Optional Rules" or appendix of the core books.