Other than the EHCR all of the mechanisms mentioned are chosen by the government to assist in the process of government decision making and, if they are 'bogging' the government down, it is a fault of that government (whether Tory or Labour) rather than the mechanisms. IMO this is preferable to the sort of situation that we had when Thatcher was in charge and she ignored cabinet responsibility or decision-making (a bit like Blair and his 'sofa government) or the sort of situation that the US currently has where Trump rides roughshod over the mechanisms within the constitution, or even the issue that may arise if Farage ever got into power with the ragtag bunch of chancers in Reform. I can see why Cummings, from his experience as power behind the throne, dislikes the idea of someone diluting his influence.
The EHCR is a separate issue as it is an external influence that UK governments have historically signed up to, and I fully understand why the arch Brexiteer dislikes it.