Can I improve my ratings ?

I have 237 trips . Coming from Shipt with over 8k orders delivered and 4.98 out of 5 rating… on Spark I’m a 4.8 and have no idea what I can do better. Every time I’ve attempted to reach out to a customer about substitutions they never respond. It seems like it’s best to let the app do the talking. Meaning just select a sub and see if they accept it or not . If I do not hear back from them I just grab the sub . When I drop off I sometimes knock and ring and just follow the drop off instructions . Again I let the Spark app handle the messaging on delivery …. What am I missing … or is this just how it is ?