It can work if you think carefully about module boundaries so that the dsls do not leak out of their containing scope. Most of the time, dsls are not well bounded and even if they are, they are likely to confuse newcomers to the codebase. Of course, whether or not dsls are used, every program does have custom dsls in the form of functions that newcomers also aren't going to understand so it isn't as though programs written in a vanilla host language don't have many of the same comprehensibility problems as those written in a dsl.
That being said, not every piece of code needs to be accessible to everyone. Dsls allow you to create a hermetic world inside of a programming environment in which certain properties always hold, even if the environment does not guarantee these things for you. Programs written in the right dsl can be more productive to write and have much lower overall operational costs. But the price is that the rules of the dsl are not necessarily the same as the rules of the host language and this leads to confusion. For the truly ambitious programmer, it can be worth sacrificing accessibility to the median coder to build systems that the median coder can't even conceive of. Of course your reward is to be derided for not expressing the solution in a language they can already understand.
Wrt to Forth itself, Chuck Moore has pointed out that Forth is a multiplier: it makes good programmers better and bad programmers worse. I personally care more about the former property and frankly don't want to work with bad programmers anyway.
> Perf teams on operating systems do things for systemwide performance with small percentage wins all the time.
And they evidently spend very little time on the things that would actually improve the lives of their users in macroscopic ways. The fact that our dominant model of an operating system is essentially c + shell is a tragedy. The operating system does almost nothing for us to help write fast, correct programs in a reasonable amount of time. It is of course for this reason that unix itself has barely improved in a material way in 30 years except in these kinds of microbenchmarks. Third party tooling and languages have of course improved, but largely to cover the gaps that the operating system has largely failed to address in a meaningful way.
This question is impossible to answer in a vacuum. What if the language made developers 90% more productive or 90% less likely to introduce a memory bug or offered 3x faster compiler times? A 1% runtime performance hit would be well worth it if that were the case. Perhaps with the extra time available, developers could find better algorithms/ways of expressing their programs that would ultimately lead to faster runtime performance on average even with the 1% hit in certain microbenchmarks.
That being said, not every piece of code needs to be accessible to everyone. Dsls allow you to create a hermetic world inside of a programming environment in which certain properties always hold, even if the environment does not guarantee these things for you. Programs written in the right dsl can be more productive to write and have much lower overall operational costs. But the price is that the rules of the dsl are not necessarily the same as the rules of the host language and this leads to confusion. For the truly ambitious programmer, it can be worth sacrificing accessibility to the median coder to build systems that the median coder can't even conceive of. Of course your reward is to be derided for not expressing the solution in a language they can already understand.
Wrt to Forth itself, Chuck Moore has pointed out that Forth is a multiplier: it makes good programmers better and bad programmers worse. I personally care more about the former property and frankly don't want to work with bad programmers anyway.