Since you're ignorant (technical meaning, not derogatory) about ASL - and signed languages in general I'm not sure how you've come to that conclusion as it's actually very incorrect.
Firstly - ASL is actually VERY suited for groups settings and in many ways is much EASIER to use in larger groups, especially those in noisy environments, than spoken language. Obviously (as a hearing person, who's recently become deaf) you've never socialized with a group of Signers in a social situation to observe this in real life and thusly are basing your statements on what you envision in your head (much like you envisioned being able to SEE soundproofing in building, when this is in fact not commonly the case at all).
Secondly - you'd be surprised how many people in concert/music/loud settings use ASL, or at least basic signs to communicate as it is MUCH easier to see across distances, isn't effected by noise, and is silent (allowing instructions to be passed between those in a sound booth and recording room without having to do a re-take).
I get that you've been involved in helping your church and others with concerts and sound - however this is NOTHING like real backline or concert audio in a professional situation. What you've experienced is what most of us (music industry) would call "modified basic" - ie taking the absolute basics of A/V and using entry level products to mimic "the real stuff" (unless you've been touring with a major label band, or working in a professional recording studio).
You may be "very experienced" for an 18 year old ... but a lot of things are learned through time... which cannot be rushed. You can study up as much as you want - but the only way to become experienced in something is doing it day in and day out for years - decades THEN (with hard work, good mentors, appropriate instruction and apprenticeships and doing the same thing a few thousand times a year for years) THEN you will have the knowledge base to back the "stuff" you claim.
Again - I'm honestly not trying to be rude, or discourage you - just remind you that you're total life experience is 18 years (which is less time than I've actaully been signing, less time than I've been doing pro-audio, mixing, mastering, recording etc)