Not accepted by who? It is speculative, but seeing as we don't have hard evidence of the source, it remains a very valid theory.
> A group of 27 prominent public health scientists from outside China is pushing back against a steady stream of stories and even a scientific paper suggesting a laboratory in Wuhan, China, may be the origin of the outbreak of COVID-19. “The rapid, open, and transparent sharing of data on this outbreak is now being threatened by rumours and misinformation around its origins,” the scientists, from nine countries, write in a statement published online by The Lancet yesterday.
[1] https://www.sciencemag.org/news/2020/02/scientists-strongly-...
> He [Aylward] pointed to humped graphs of cases over time—they are the shape of an epidemic that has been hobbled, he said. Disease spread has been in decline since the beginning of the month, and doctors in China are honing their ability to treat patients. “If I had COVID-19, I’d want to be treated in China,” he said candidly. [1]
> There’s plenty of reason to doubt the official numbers—Chinese officials initially covered up the virus and arrested whistle-blowers who tried to expose the outbreak. Aylward acknowledged these concerns on Monday, but added: “The decline that we see is real.” [2]
[1] https://arstechnica.com/science/2020/02/coronavirus-spread-i...
[2] https://www.wired.com/story/could-the-us-contain-a-coronavir...
> Scientists from multiple countries have published and analysed genomes of the causative agent, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2),1 and they overwhelmingly conclude that this coronavirus originated in wildlife
The person you're responding to above says that the lab has been collecting samples of SARS-like viruses from wildlife for study, and conjectures that maybe one of those escaped from the lab. That possibility is not contradicted by the statement in the Lancet.