I think what the GP means is that if you speak in grammatically correct sentences and are intelligible, people are less likely to complain or look down on you. I.e. that's a deliberate choice on the listener. If your pronunciation is so off that your listener can't understand you then that's something that's outside of their control; either they pretend to understand and go "uh-huh", or they have to ask you to repeat yourself.

>My understanding is that everyone's brain is wired to expect a word in a certain way and unless you have encountered other accents, the speaker has to repeat what they have been saying.

Nah. People get used to understand certain sequences of sounds and eventually get used to your particular accent, even if initially they had no idea what you were saying. One time I had to work with a Vietnamese woman (let's call her Anna) who said "transaction" like "trunsun" or something; definitely one syllable too few. After several months I was quite able to understand most of what she said, although occasionally I needed her teammate (Barbara) to translate for us. To restate GP's point, both Anna and Barbara spoke grammatically correct English and had definite East Asian accents, but Barbara pronounced things correctly and Anna didn't, so Barbara was easier to speak with, while when speaking with Anna I often had to ask her to repeat herself.