I think it would be very rare from me to decide on the number first and then decide what the character is. I would probably think something like, "The blacksmith should be strong... human? No, I'll make him a mountain dwarf and make him even stronger." Then I would set the strength at 18, while if I had stuck with human I would have set it at 16. Because in my world, and in the default D&D setting, mountain dwarves are stronger than humans. And I know that humans get a +1 strength, so technically the dwarf should only go up to 17, but the exact score doesn't matter. What matters is that mountain dwarves are stronger than humans on average.
But that makes perfect sense. If you take it away the halfling, elf and tabaxi aren't any of those things. If they have a +2 dex you then need to decide what that means for that race. If you take it away then... nothing. There is just nothing there. The are not any of those things. And dwarves aren't hardy and half-orcs aren't strong. When it comes to strength or intelligence or wisdom or constitution, etc. the races are all the same. And that is not a good thing. It is boring.
See, you are just working under a completely different set of circumstances. You decided he was a dwarf just to make him stronger, but if I wanted him stronger... I'd just make him stronger. I wouldn't just make him a dwarf to make him stronger.
And you've said those races are nothing without those +2 Dex scores, but you are missing the point. +2 Dex is meaningless. It means speed, it means grace, it means clever fingers, it means skill at archery, it means whatever we need it to mean, but it can't mean the same things.
No one, absolutely no one would say that Goblins are as Graceful as Elves. Elves get +2 Dex, and that means they are Graceful. Goblins also have +2 Dex. But they are absolutely not graceful. So... +2 Dex doesn't mean you are graceful. It can't, because everyone else with that +2 Dex isn't graceful. Only Elves are.
1) This is true. The Tasha's rule is optional, and it leaves the static racial ASIs in place. I am for this. I think that is a good solution. It answers every possible complaint. Unless there is one I am missing?
2) So it sounds like we are agreeing then. There should continue to be default ASIs, proficiencies, languages, and all the rest to model traditional depictions of fantasy races (species), but exceptional individuals (PC and individual NPC) can break that mold and be unique. Sounds like a win-win to me.
1) Then why did you say Tasha's was removing proficiencies if you don't think Tasha's removes anything? You seem to have not realized your own statement.
2) So, this has a few levels. Firstly, everything for Dwarves and Elves and Halflings ect ect ect, is completely written. Nothing done in 5e is going to erase those defaults. So if you are worried Dwarves will no longer have defaults, just open your PHB, because they are right there. Secondly, you seem to agree that changing a PC doesn't change the Race, so there is no problem. But thirdly, I don't think we need to continue to have default languages or ASIs for every single lineage going forward. We have floating ASIs and Floating Languages already. High Elves get +1 Language. +1 Language is fine. So, if a new lineage is designed with a floating ASI and a Floating Language? Then it is fine. Because this new lineage has been designed this way. Their default is this design. Say we need a default ignores the fact that this is also a default.
Actually I think it is great that Humans get a +1 to everything. Now they they are slightly worse at what other races are best at, but slightly better than what they are not good at. It makes it so that, overall, humans are just better at everything. Which, as a human, is nice to think.
Plus if you follow your logic, halflings used to be weaker than humans because they didn't get a bonus to strength. Now they are weaker because they don't get the +1. So they reduced the penalty by 1, but they didn't actually get rid of it.

It doesn't quite make sense that hill dwarves have a "-1" strength (in comparison to humans), but we all know the system isn't perfect.
Right, this system isn't perfect. It is already a mess of contradictions. So acting like changing things is suddenly creating contradictions that never existed is just false.
Humans are worse than the best, as good as their second best, and better than their average. But, we think of humans as the average. The 3d6 Bell Curve model was based off humans getting no bonus, so changing that situation as changed every assumption.
This doesn't make any sense. Because some things are inaccurate or contradictory or were updated, we should just throw out everything? The whole, "throw the baby out with the bathwater" thing?
Some things? Just about every single monstrous NPC is wrong. Multiple PCs are only partial. You are accusing me of throwing out a baby, but the very existence of a baby within this bathwater is questionable.
Saying "this must be true because it is on this chart" is very weak when you can easily point out that the majority of the chart is wrong.
It does change them. I'm not saying it breaks the game, but it changes how the race functions and how it is viewed. If it didn't, why even bother removing the -2 intelligence penalty for orcs if it doesn't matter? And if something is changed and updated and you think, "Okay, they changed lizardfolk. Well I guess they just wanted to portray them differently." Then there is nothing to get upset about. I think removing the -2 intelligence penalty from orcs in Ebberon makes sense, because they are portrayed differently than in "default" D&D. But there is also nothing wrong with having a more simpleminded brutish orc in D&D either and representing that with an Int penalty.
I'm not rehashing that debate. There is a very clear difference between having a penalty and being able to float your bonus.
And the point I was made in there was hiding in your post. If they changed every single monstrous NPC in the chart when they made it a PC, then why would I assume that the Monstrous NPC on the chart is accurate? None of them were accurate.
And I think you are skipping past my point that default racial ASIs tells us that the dwarven species is tougher in general than other humanoid species. Any individual can be an exception, whether a PC or NPC, but in order to be an exception there has to be a standard.
What is the default for a Human commoner? 10 Con. Dwarves are tougher in general with 12 Con?
I've got a DnD beyond game pulled up, let me just post this real fast
Human -> Con 12
Human -> Con 14
Kalashatar-> Con 12
Kenku -> Con 14
Aasimar-> Con 15
And I'm actually shocked to see those two 12's. The average I see on players is 14. So... if Dwarves are exceptional for having a 12, and most PCs have between a 12 and 16... are dwarves really exceptional from the player's perspective? They have the average lowest values that I normally see.
So, what defaults are we comparing too? 10? 12? 16? Is the default the human commoner? The 12 that is the lowest score most players have for their "average". The 16 that is the default for their prime stat?