Uh We were talking about a game with a level cap of 10 (at least I was) like Bg3 but yeah, for high-levels a full caster will always be superior to dabblers like rangers as you said, of course. Warlocks, bards or sorcerers could make them work for their money, but ultimately specialists would be better at what they do, if only because they could reach the heavenly 9th spells. You are absolutely correct, nothing to say against.
PD: maybe rangers do not have raise dead or remove curse, but pallys and bards can wink warlocks could cast remove curse too. And to be honest, I´m in love with healing spirit and goodberies, something that clerics lack but I concede a druid would make better use of it than a ranger. Other classes will offer interesting variants that clerics or wizs cannot do, like metamagic or warlock casting.

In regard of spells I concur.

I will add to your statements that a bard (even more lore bard), an artificer or a rogue over level 11 would run in circles around any other character if we measure only skills and tools`competence; in quality and quantity.

First I have to point out yet again that I didn´t mean a class could do the same as the other, I said they could make the same role that other traditional class usually did in previous editions: healer, scout, face, sage, etc. And many of those do not rely on the number and quality of spells you can cast.

In the matter of skills and physical combat all classes are more capable than in previous editions and the difference in competence is not that much. At least in comparison. Many characters could be built to fit the role of frontline fighter, marksman, trap disabler, scout, diplomat, thief, survivalist, know-it-all, etc using classes that were simply not fit in previous editions.(see all the examples above)

Heck, after 5e you have to pick a rogue, artificer or have a cleric and a wiz with a bunch of scrolls of lock if you wanted to deal with traps & locks, now any character could be trained to do it; and some of the best combat and tank builds in 5e use moon druids and warlocks as a base, the most popular without a single level of a traditional warrior class.