I mean what does "put you at a disadvantage" even mean concretely? To use a less popular language, it means you need to load up context related to the semantics of your language, load context on how to invoke tools to make sure the syntax with your language is correct, load up context related to each tool call you make (which will be more numerous in a niche language), and load up context on architectural decisions that might be specific to your language. All of this is simply a token cost. By forcing a model to load an initial amount of context per harness turn you also effectively shorten the max context window beyond which the model becomes stupid (which itself is much shorter than the max context length.)

Obviously it's not like people are specifically trimming each and every prompt they give a model to tokenmax their models to get the best output / input prompt, we instead live in a spectrum of how many tokens of input and context we're willing to provide to a model to make progress. If the cost of those tokens is low enough for the problem domain you're working in, then it's fine. For some the readability of a personal language may outstrip any of the token costs that one needs to pay to use it. Alternatively maybe you want something like an array language (J, K, APL, etc) which allows array programming and optimizations that conventional PLs just can't do. Maybe you want your language to compile to a target that is highly portable. There's actually a lot of stuff out there that previously wasn't feasible but with LLMs-as-force-multiplier absolutely is.

I also suspect the space is a continuum. There may be pareto optimal points, such as DSLs built atop languages, that are both highly readable but also fairly token efficient.