loop() functions call
delay() then of course that will delay getting to the next function and will slow down the whole process.
The only way to deal with that is to rewrite the code, combining what you're calling and fixing it so that it takes into account the other work it needs to do.
Same thing if you call any blocking functions, like reading from
Serial until you get a newline.
If that's not the case... well, the ESP8266 is a small, not particularly fast processor. If there are no delays or blocking functions then your code is running as fast as your code might run and you'll just have to live with it.