This is perhaps doable in a very early stages where the team is just a few people and there's little tickets and customers, and perhaps the customers are also tech ppl/early adopters, so they'll appreciate talking to someone who knows all the details - but as soon as you grow a bit this becomes just unsustainable.

First, engineers cost a lot of money. IME 90% of support tickets quickly boil down to a few same questions repeated over and over, and with a proper knowledge base in place anyone can answer them. You certainly don't want to pay engineers to do it. Second engineers hate dealing with customers because most of those problems are stupid and repetitive. You'll be both loosing money and employees. If there's an unknown issue, then escalate it to the engineers, but let someone less skillful/easier to replace do the triage first.

That said, you definitely want your support to have technical/domain skills, because nothing is worse for a customer than realizing that you talk to a person who knows less about the app than yourself, and keeps sending you back the predefined template answers, just wasting your time. I left more than one SaaS because of such (lack of real) support. So put your interns/juniors there for onboarding. They'll learn a lot about the app, customers will get good support, win-win.