I feel like a failure to my son

My son is 5 years old and is in kindergarten he’s been going to school since he was 3 year old due to Massive speech delay he was determined at three years of age to have the speech of an 18 month old granted over time it has gotten better but school is still having a hard time understanding him he goes to speech two times a week and having to wear a mask all day is not helping since he gets frustrated easily to where he cries because the teachers can’t understand him all the way, we were told it all is happening because from the age of 1 to 4 he has had chronic ear infections to where he’s had his adenoids removed, tubes put in 3 times and his tonsils removed. I feel like a failure to him as we do a lot of home to help but he’s still having a hard time.