Based on your post, one might conclude the following. The Russian Empire had no right to expand or do anything else a classic empire would do, but you would understand and excuse the British Empire's expansionist moves in Caucasus and the Central Asia.
And you would be wrong to conclude that.
Every empire is by its very nature oppressive.
That doesn't mean that every empire is necessarily an evil through and through.
The more successful empires stay on because they somehow incorporate those whom they subjugate into the empire and maintain a stable rule that is good for business. Leading to a higher living standard and increased opportunities for the population as a whole. - Like the Roman empire. And no one will accuse the Romans for being great humanists...
To look at the Russian, Roman, British empires with modern eyes, is IMO silly.
We have to, the best of our abilities, look at them with contemporary eyes.
The Romanovs were not toppled by an external uprising, leading to an invasion of Russia, with the ultimate purpose of freeing the conquered territories.
The Romanovs were toppled by an internal uprising, that had been brewing for many years - and
that's the context we have to study this, not execution, but lynching of the Imperial family.
So let's look at Russia anno 1900.
The vast majority of Russians had no political influence whatsoever.
The vast number of Russians lived in, even for the time, deep poverty. With little prospect of improving their life through hard work or even initiative, not even for their children. (The American dream.)
The vast majority had few rights and even less opportunity to exercise those rights.
Peasants were by now able to move freely around selling their work to the highest bidder, not that it meant much. They went from serf-like condition in the countryside to serf-life condition in the urban factories.
The vast majority received little or no schooling whatsoever. And what education they were taught can very much be boiled down to: Do as you are told, don't complain, endure and get your reward in Heaven.
There was nothing remotely resembling a social system in place. Such systems were being introduced elsewhere, but not in Russia.
That's just to mention some of the major problems.
What is worse is: There was no genuine wish from the top to implement major reforms, not until forced to do so.
That's a problem in an absolute monarchy!
Instead it's my clear impression that Tzar Nicholas was scared of the oppressed masses, and genuinely resented reformers, blaming reforms for the tragedies in his own family.
At the same time there was even less will among what you can call the peers of the Imperial family. I.e. the noble, ultra rich top class of society.
Instead they continued living their absurdly rich lives, closing their eyes for the fact that they had become anachronisms and were destined to go extinct.
Their behavior is typical of society based on slaves, they are indifferent to the plight of their slaves, while living in fear of the slaves, which means they oppress their slaves more and more.
That's how the Romanovs and those around them IMO saw their world. It was a Dance Macabre and the dance ended in a cellar...
If you are not willing to adapt and to conform to new condition, you will go extinct, it's only a question of when.
The Romanovs were neither willing, nor able to adapt.
I will even go so far as to say that people living in the Russian colonies were better off than the Russians themselves. They manly continued living more or less like they always had, with whatever flaws and advantages their societies offered.
Don't get me started on Victorian Britain!
It was a super capitalist society, where human suffering mattered much less than profit. (The Irish Potato Famine and the conditions of factory workers.)
It was also a society where not only the physical, but also the psychological distance between top and bottom increased.
However, at least the common man in Britain had long established rights and knew his rights. He could, albeit with considerable difficulty, rise by merit.
He could, and he knew he could, seek a better life for himself in the colonies or by immigrating.
There was a growing middle class, instilled with typical Christian values, like charity, moral norms and concern for your fellow human beings, even if that concern only went so far. - There was little of that in Russia.
In my unscientific opinion it was the growing middle class, and the growing wealth and influence of the middle class that saved Britain from a revolution during the 1800's, not the monarchy.
ADDED:
I see you added a sentence, which I don't quite understand. Are you saying my opinion expressed in my previous post is shared by many? Or...?