Normal speech development for 2.5 year old

My son was born May 2017 and can say a good amount of words. I understand him 95% of the time and every now and then he will say something that I just can’t understand. The other words I do understand aren’t pronounced exactly correct but I can understand them and so can dad. Even his grandparents can and they only talk to him on FaceTime. He follows multiple directions, he understands when I talk to his father about certain things. Say if I tell his dad I’m going to the bathroom or we’re gonna go take a bath or go bye bye he starts preparing. He will go to the bathroom before I do to follow me. He will go to the stairs to take a bath and he will even look for his shoes when we talk about leaving. The only concern I have is he doesn’t pronounce things clearly and he can’t really count (he tries), can’t say ABCs, but knows his colors, shapes, and every animal or name of certain vehicles or planes. He knows body parts and foods too. He also cannot say 2 word sentences. When we try, he kind of gets frustrated and will say somethings backwards. Like “my ball” comes out as ball mine. I’ve told the pediatrician and she keeps putting it off. I told her this at 24 months and she said to wait 3-6 more months but it didn’t really improve that much. I’m worried he should be getting help but idk if this is normal or not. I don’t know any children this age and the ones I see on YT are far more advanced. We read to him, we explain everything to him, he has wood puzzles, and a lot of educational toys. I’m really trying my best here but I think he needs more. What do you think?