I've been writing about this topic for the last 7 months. The absolute biggest change you can make within the confines you presented is to switch from "looking for weaknesses" to "looking for strengths". I wrote about this here during the beginning of the year[0].
You can find all my past articles[1], and I'm happy to find you specific ones. I think, given that you can't switch away from algorithmic interviews, at least make the interviews more collaborative, define your expectations up front, and generally find ways to help the candidate show their strengths.
[0] https://hiringfor.tech/2020/02/10/false-positives-and-false-...