I struggle with tooth brushing as well, although don’t feel quite the revulsion you describe. What has helped me lately is my step counter — rather than standing at the sink, I walk around while brushing, up and down hallways, around tables, etc. Not exactly “fun”, but it takes the focus away from the icky gum sensations and can be a self-imposed challenge each time to change up the route and increase the number of steps (also helpful for the daily count — during Covid, it’s not easy to meet a step goal!). Works for me… might or might not for you.