I mean to say that these haplogroups are an excellent way of representing various lineages among the races and subraces of our world.
For instance, we know the Nords are a mixture of indigenous, western, and eastern Europeans; that the Brythonic Celts are quite unilateral in their lineage; that western Slavs, or Wends, split from eastern Slavs and differ from them thusly; that Bosnians are an isolated and relatively unmixed remnant of the indigenous Balkan peoples; and that Ukrainians have a far higher mixture of indigenous blood than Russians, making them indeed racially different.
The point is that we aren't just a collection of people who happen to be similar, but rather a living legacy of those who came before, and that haplogroups are a useful way of measuring this legacy on a grand scale.
Individuals' haplogroups are not useful for measuring this, but take them by the thousands or millions, and they indeed are.
Why should I care what tiny variants a group of families bears in their genetic code if I do not know the context of their histories or their phenotypes?
Haplogroups are indeed useful to track ancient migrations, but still
VERY insufficient and certainly less relevant than autosomal DNA admixtures, especially if your goal is not to understand the ancient movements of peoples, but to understand the most relevant population admixtures that contributed to what a certain population is like nowadays. In just 6-8 generations (less than 200 years), provided that the men with a certain Y-DNA haplogroup are surrounded mostly by women from another population structure, it's totally feasible that you end up having men belonging to the typical Y-DNA haplogroup of an ancient people A while at the same time the bulk, i.e. 90%+, of their ancestry (autosomal DNA) comes from the ancient people B. Yet if all you care about is Y-DNA haplogroups you won't see the true and
muuuch bigger picture. Also, Y-DNA haplogroups of course don't tell us much about the "other" decisive 50% of a people's ancestry, because women don't have them. Let me just give you one small example, maybe you'll see what you got wrong in your observations of the genetic history of some peoples:
1860 - Han Chinese man (Y-DNA O3) has a child with an English (100% Northwest European) woman: John (Y-DNA O3, typically East Asian; ~50% East Asia, ~50% European)
1885 - John has a child with his Scottish (100% European) wife: it's a boy, Richard (Y-DNA O3; ~75% European, ~25% Asian)
1915 - Richard has a child with his English (100% European) wife: it's again a boy, Phillip (Y-DNA O3; ~87.5% European, ~12.5% Asian)
1940 - Philipp has a child with his Iris (100% European) wife, Sean (Y-DNA O3; ~93.3% European; ~6.7% Asian) ----- In 80 years, you have an overwhelmingly European male (> 93%) with an East Asian Y-DNA haplogroup. Is he "Han Chinese"? No, of course not. He had some non-interrupted male lineage starting in a Chinese man, that's what it means.
What I say can be demonstrated very typically with the haplogroup R1b: R1b-V88 probably came from Europe or the Near East, yet if you go to Chad or even Mali you'll see
millions of men carrying R1b haplogroup, but with a really minor West Eurasian/European-like admixture, the bulk of their ancestry, what really makes them what they are, is Subsaharan African. The same process of autosomal dilution combined with a clear dominance of some Y-DNA haplogroups happened much more recently in the Americas, where you can now find millions of mainly Native American and/or African people with "European" Y-DNA subclades of R1b, I1, I2 or J2.
I really think that you're making one of the most common mistakes that newbies in population genetics do (I myself did that
a lot a couple of years ago), which is overestimating the relevance and the historical/genetic meaning of Y-DNA haplogroups. The way you're interpreting genetic data and Y-DNA haplogroups in particular is undeniably leading you to wrong conclusions. Just to give you one example, no, modern Balkanic peoples like Bosnians
are not the remnants of indigenous Balkanic tribes from many thousands of years ago. You're again conflating
overall ancestry and
paternal lineages (not that Bosnian males all belong to truly Mesolithic haplogroup I, anyway). That won't help you to see the whole thing. Without any intention to offend you, just an advice, let me say: you should need some of the fundamental genetic studies, many of them linked in the post Angela provided some posts above in this topic. You'd benefit a lot from learning more about population genetics and gradually realize your misconceptions.
Also, I fail to see the connection between your points above and Atlantic Megalithism being necessarily related to R1b men. We are not denying to understand the history of peoples when we point out that
probably (not certainly) the Atlantic Megalithic cultures were not peopled
mostly by R1b men, and that that region of Europe underwent profound demographic changes since then. That's not erasing history, that's trying to see it as it really was, irrespective of the desires and interests of present-day people. Would those populations be less connected to their ancient history if they suddenly found that in a cumulative process along thousands of years the males that transmitted their Y-DNA haplogroups mostly came from abroad as immigrants? Would it somehow be offensive or demeaning to them? That sounds like, firstly, underestimating the genetic contribution from women, and secondly a certain kind of wishful thinking very common in nationalistic circles, where people
desperately want to believe that their people are primordial, indigenous, with very ancient roots in their present-day lands, even when that is totally contrary to the archaeological and genetic evidence.