I don't understand the argument for renewing the Coronavirus Act in its current form. Surely the initial justification was that it was a situation where the virus was not well understood and the government needed to be able to pass legislation "with immediate effect" because of the unprecedented nature and urgency of the situation? That is no longer the case - we are 6 months down the line - and a lot of the public confusion is being caused by the announcement of snap measures which have not been fully assessed, which are then changed, repealed, amended or extended.
I'm not a conspiracy theorist and wouldn't frame this as a power grab, but if the government were to extend the act in its current form it does appear that they are attempting to avoid parliamentary (and thus public) scrutiny.
There is no reason why new laws cannot be debated in a timely fashion. We've seen, for example with the Syria bill, that the government were able to debate and pass legislation very quickly. There is no reason why this government couldn't do the same with new Covid laws. I don't think there is anything which now needs to be enacted so urgently that it cannot wait a few days for a debate and a vote in the House.