"Whether you like it or not, the tide of history is moving from smaller to larger groups."
Things tend to happen whether anyone likes it or not. That is not really specific to me.
You are right about the tide of history of smaller groups moving to larger ones. Possibly the eventual world will be one giant entity with some form of feedback loop for governance that allows for greater say by the populace on how that governance is manifest. Checks and Balances and Divided government and Voting will certainly be parts of the equation if such a government could exist.
In the interim however, I think there is a counter movement toward smaller units gaining more say in their own affairs as larger entities are formed. Even in my own community which is a small town, we seem to be gaining more autonomy over certain aspects of our governance even in the face of larger overarching governance. The state provides the overarching rules, but within those rules it is the local government that determines how such rules will actually be implemented.
"I really could not care about how the UK was not created well. It can work well nowadays. 1745 was a long time ago."
Certainly the past is the past. The UK was formed in the way most large nation states formed back then conquest. That is fine.
I think more pertinent to today is the question 'can a group have more autonomy if they feel their needs would be better met by smaller governance'. It seems to me that the argument has to do more with the idea that many of the Scots would like more say in their own affairs today. But like everyone else they also seem to want to be part of something bigger in retaining membership in the EU. Belonging to a bigger geopolitical marketplace won't be such a problem for the Scots if they choose to have greater local control over their own affairs in my opinion.
"The UK is not perfect but neither is my car. I won't make my car work better by sawing bits off."
This is analogy seems a bit off point to me.
Separating the 2 countries is not like lopping a baby in 2. It is more like separating a liver. Both parts can function and grow separately of one another because both are fully functioning even though both will have diminished size from what the whole was. Both can grow to have economies that are larger and function well also.
"Despite what the SNP tells us, if Scotland leaves the UK, it leaves every alliance the it is in."
Not really. Scotland will get to pick its own alliances and reframe how those alliances are formed is all. That means greater liberty to follow ones own course in my book and is a net positive. Every alliance formed for the UK will be revisited by all of the parties for similar terms with the Scots. Who knows, I can see scenarios where the Scots will have opportunities to form even broader alliances with parties the UK won't form alliances with.
"It will be able to apply for entry but this is not a fast process and meantime, we are outside."
I think it will be more like a rubber stamp or somewhere in between that and new EU member applications. Scotland is already in the EU as part of the UK.
Some specifics will need to be worked out, but the process will not be very lengthy or even likely inconvenient. I could see the EU giving the Scots a tentative waiver for many functional things so the transition won't be too disruptive. The EU is hoping for a greater level of stability. It is not in their economic interest to keep the Scots at arms length. They are a know quantity. The EU will avoid throwing even more chaos into their western borders in my estimation. It is in the EU's interest to move to lock down stability with Scotland rather than create greater problems.