Whether you write unreadable code or not is not a function of language. This is a lazy attempt at criticism. My preference for Ruby is in part because reading and understanding well written Ruby is a joy compared to every other of the dozens of languages I've used.
And since (un)readable code is not a function of language, you cannot state in your next sentence that reading well written Ruby is joy in comparison with other languages.
Of course I can. There is no contradiction there. You can write readable code in any language, even assembly, but that does not mean well written code in a language that is also particularly readable won't be more of a joy to read than well written code in a verbose or hard to read language.
> The first statement is provably false, empirically, as huge systems are overwhelmingly not written in dynamically typed languages.
Your conclusion is not supported by the claim you try to support it with.
> Ruby is not one of these languages.
You're free you think so, but you've not provided anything but unsupported conjecture and logically invalid reasoning to support your belief, so rather than convince me, you've provided an additional reason to question your judgement.
What do you mean by huge systems? Many of the largest web platforms were indeed built with dynamically types languages. And these days Javascript somehow ends up being used for almost everything you can think except an OS kernel.
Your team mates probably object to that ease of writing, as they did for Perl 20 years ago.