The very short answer is that imperialism requires very specific economic systems and incentives. Those systems are not going to occur in socialist States because socialist States develop different economic systems than capitalism because the profit motive is absent, which impacts short term and long term economic development plans in many significant ways. For an extreme example look at Juche's emphasis on self reliant socialism within an internationalist socialist order. They cannot do imperialism because all of their economic planning is built around a stable self sufficient economy. An extractivist economy isn't just something you can graft on, it has to be a central part of an economy to make economic sense.

For an example of socialism not being imperialist when it has the opportunity to, you can look at China forgiving loans. It doesn't do so out if the charity of its heart, it does so because it is incentivized to because damaging other nations self determination through financial coercion actively harms its project. It wants strong neighbors with close economic ties, it doesn't want to suck the marrow out of their bones because that is destructive to China in the long term, and socialism is able to plan in the long term unlike capitalism which has to be more short term oriented because of the way its incentives function.

Imperialism is actually a very costly affair (in many cases it costs the home country and only benefits specific lobbyists within that country) compared to mutual cooperation and always rebounds on empire, it only happens because of market failures that do not happen under socialism.

Socialism’s goal is to provide for its people by moving past a society based on exploitation. This is why it wouldn't engage in colonialism.

I think you'd need a different word to use to describe your socialist-colonialist state. Imperialism doesn't mean, "when you invade".

Imperialism is the monopoly stage of capitalism where finance capitalists export capital rather than commodities and these capitalists become the most dominant.

There's many different capitalist interest groups, but one is by far the most powerful and dominant in global politics, the finance capitalists. This group of capitalists always come to dominate over all others, most capitalists require access to financial capital to expand their businesses, or to weather difficult circumstances in the marketplace. Financial capitalists gradually gain control of all industries through being able to see the movements of each industry and by them being the spider in the web, put simplistically. Then when they've run out of domestic exploitative growth opportunities they reach out beyond their borders and team up with other financial capitalists through mergers etc. This is imperialism, the final stage of capitalism. All capitalism eventually ends up here. Russia will too, but not yet.

The major capitalist interest group in opposition to the finance capitalists are the always losing group of industrial / national capitalists. These are private owners of domestic industries who mainly derive most of their profits from operating within the borders of a particular country (or the EU or whatever). Donald Trump would be an example of one of these, and he'd be in political alignment with many other industrial capitalists, Elon Musk, Jeff Bezos, Bill Gates... "industry leaders". Their politics tend to be libertarian in nature, the social conservative aspect of their politics is just a front they put up to gain the electoral support of naïve socially-conservative people and exploit them. They don’t really care about religion or guns or anything like that. They usually like traditionalism because it provides them with a reliable exploitable source of labour. They would have opposed women in the workplace until they realised they could exploit them too without risk. Same with LGBTQ+ stuff, they used to be opposed but are now less so. They still are in Russia, indicating their capitalist immaturity. The western capitalists have grown beyond this stuff to some extent. A lot of conservative politics comes from this group. The Finance capitalists are less well known. You know the names of many western finance companies but probably not nearly as many outside the west.

Russia is an example of a country emerging from a primitive stage of capitalism that stands opposed to western financial imperialism. They are largely in control of their economy and government after western financial capitalists pillaged Russian industry after the fall of the USSR. This is upsetting to western finance capitalists, who desperately want to destabilise Russia and would love to install a government that is friendly to western finance so they can pillage it again. it slipped out of their grasp with Putin after Iraq, they want it back.

It's western finance capitalist imperialism versus Russian industrial capitalism. Putin is the Russian industrial capitalist's thug godfather. If any of the oligarchs step out of line and try to sell out mother Russia, they'll find themselves defenestrated quick sharp. If he falls then they all need to quickly put someone else in place to rule over them and protect them from each other. If the US gets a foot in the door again they're all fucked. It's constantly knocking.

Russia's industrial capitalists have already been raped by the US twice before now, they trust Putin as their administrator. He lets them do what they want as long as they don't fuck over Russia. He's a dictator, but one that prioritises a strong and functional Russia over one that collapses to be strip-mined and sold off by NATO capitalists. Given the lack of real alternatives (the Communist party was outlawed for a time), Putin has clearly been the only real option for Russians for most of the past two decades. They will not be pillaged a third time, hence this completely predictable Ukraine reaction they'd hoped for after constant provocations, the last one being the Nazi led coup and overthrow of Ukraine's democracy by the Right Sector Nazis and others. The one thought experiment that no lib can answer is what the USA would do it the shoe was on the other foot and Russia was arming nutcases in Mexico.

You're hearing "imperialism" a lot right now because it's been inserted into the discourse as a wildcard term to con people into explaining away the motivations behind Russia's invasion, instantly dismissing thought of all of NATO's provocations. It would probably take Russia decades more to become Imperialist, maybe I'm wrong, maybe it would take less time but it's not now, and "imperialism" is not the reason for the invasion by a long stretch.

Interesting. Do you have an example of such later writings?