Somewhat of a curious question and more academic than intellectual. I suspect it was a question the recipient thought more about than the person who stated it, stingray probably just writing off the top of his head without pre-preparing for a a factual discussion.
Like when people say "we haven't had a very cold winter for, like, five years now". The truth of the matter is probably that its close to being a correct statement, but it could well have been 4 or 6 years, or maybe there was one very cold winter 4 years ago but all the others have been warmer. The statement results from a general feeling but is expressed factually because it's how people say things. People don't tend to speak always in hard facts.
But, yes, it is the kind of statement that makes for an interesting topic whatever the fact of the matter is. To ask why it is that someone has that general feeling regardless of the fact of the matter.
The reality is you could ask the same question of practically every country on earth. Poland hasn't made a great RPG in the last 5 years. Neither has the UK. Neither has Canada. Germany and the USA have though.
This is more a question about how long modern companies take to make computer games rather than a debate about what is great or focusing on the USA in particular.
I think many of us grew up in gaming in an era when developers made a new game every year, and they did this with teams of 20-50 people and, by today's standards, relatively low budgets.
But as the demand for graphics intensified, so the development teams swelled along with the production times and the budgets to the point now where it seems like eternities between games.
Triple A games now regularly expect customers to wait 5+ years between sequels, and even double A is a guaranteed 3 year wait.
And so this filters down to the indys as well, this idea that you're not expected to 'churn out' games. Most of the quality indys take even longer than AAA games to release the next game, and its often not even a sequel or even the same genre as their first game.
I think InExile are probably the closest developer to what one would term a company that regularly puts out quality RPGs in a timely manner. Sadly, they don't make classic RPGs, but prefer to make niches of niches, just like Troika used to do, so it's not really ideal for the topic of a company that regularly makes great RPGs, but I think they're the closest example of what another developer could do. But none seem to want to do.
I suppose Obsidian are similar to inExile, but that's a longer, much more nuanced discussion really, as Obsidian never really make 'their own thing', they're a sort of cloning company, but, yeah, different discussion really.