No, he wrote grep. Before he wrote it there was no grep. And yes, he's recognized as a great programmer. With Multics, Unix, B, C, UTF-8 Plan9, Inferno and grep to his name (and probably others that I forgot) he has more than deserved that.
Future grep versions, including the FSF one, were all re-implementations.
Your statement in the GP is nonsensical.
I have a research degree in computer science from one of the best universities on the planet, I have been using Unix systems for over 25 years, have been the go to person for billion dollar companies (you know the person they beg for help), and I don't know what I am talking about?
I have even used Plan9 and the silly editor.
I probably have forgotten more than you (or Thompson) has ever known.
Thompson is an amateur, because all of his programs are of "trust me, bro"-quality. Call me when Ken (and all the n00bs from that era) grows up and implements grep in Rocq.
Yes, so you say, and I'm the pope on alternate Sundays. Appeals to authority are meaningless without identity. Meanwhile, I highly doubt you are qualified to polish Thompson's shoes, all I see is an AC novelty account making dumb claims with hindsight. Anyway, enough with you, off to the ignore list.
I do not agree he was a great programmer. All of his programs are trivial from a computer science perspective.
In fact, you can quite easily check this by trying to let an LLM generate a program like grep. It can do that. Now, there also exist programs for which LLMs can't generate code, because it's too complex.