The issue is that Japanese devs still have to follow the law in Japan so even if DLSite moved out of the country, nothing would really change for the better. If anything, more would end up censored since DLSite would need to follow the laws of their new country, and these laws could end up more strict even if they didn't require mosaics or censor bars. Some japanese devs self-publish on steam and the releases that don't end up rejected are all censored with mosaics or they sell a patch on dlsite that adds the adult content into the game, but with mosaics.
And as OriginalSin mentioned, it would probably not be looked upon too well if DLsite opened up a second branch specifically to skirt around Japanese law. You can try to break a law by going out of the country, but most of the time your laws still apply to you.
I already mentioned how little English speaking users actually spend on DLsite in comparison to the japanese userbase. The reason they even combined the two sites was because of how little people were using it in comparison. The difference was even more apparent back then as you would see a particular work hitting 5000 on the japanese side, while the english side just had 20 sales or less. Ironically, more english speakers were using the japanese site, be it to buy the works because they understood japanese (or didn't care, especially if the work was in japanese either way), or to find works to pirate. So when the sites became merged, the site saw more english speakers buying stuff (they were the ones buying before). Even so, English speakers make up far too little of sales to have any sway. The real issue isn't that works aren't uncensored, most people playing (whether they bought them or not) these kind of games have played them for years and it hasn't stopped them so far. It's that most of it is in Japanese only. Which is why DLSite has put a lot of effort into translating the games and manga over the years. You have the officially translated ones, and now you have ones put through a machine translator (which from what I saw wasn't as bad as most machine translations). Some devs also get their games translated, but the quality is all over the place as some are professionally translated and others thrown into google translate. Then there's DLsite's "Translators unite" circle which is basically outsourced translations done by users.
Ultimately though, I don't expect english speakers to ever take up a sizable portion of buyers even if everything had great translations, and I don't see it as happening even if everything was uncensored because the fact of the matter is that for most people, if it isn't on steam it doesn't exist. Other stores exist in the west, but everybody prefers to buy from steam and that puts developers at Valve's mercy when it comes to english speaking buyers. I've seen many devs try to sell on Steam but end up with their works rejected or banned. One dev Marmalade Star put in months of work to get one of their works on steam and in the end it was rejected, so they sold it on DLsite as a different version of a game they sold on there.
Steam is not softer with their rules. As I pointed out above and several times before, Valve's has consistently banned or rejected many games that should have had no problem, including ones that were published on console. People prefer Steam because of it's features and it is where all of their other games are, not because it has less rules surrounding content. Devs put up with it because they can make way more from steam users in a small period than they ever do on other platforms, even if their games get banned. This is only the case if it is a quick release. If a dev actually put in a lot of work to translate their game, then it is much riskier. As a result, you see a lot of trash and MTL releases on steam, because those are what Valve has incentivized.
