There was a poll last year (not sure if it was UK wide or specifically English) but more people were willing to jettison Scotland than NI if it meant getting Brexit - I found that very eyebrow raising, whatever your view on the plusses or minuses of Scottish independence.
I take it there must be dismay with Johson so, that he's not affording the Scottish people the chance to cut their own throats?, would solve a problem for the rest of the UK and the Scots would only have themselves to blame, job done.
The is certainly some disillusionment with SNP at the moment, some feeling they are not committed enough to push for the referendum, the Salmond shenannigans (true patriot that lad.....not), and the curious case of trans rights, of all things, flaring up. It probably boils down to whether those short term things trump the chance to choose your own government, or whether you'd hold your nose, vote SNP, vote Independence and then set about putting the (Scottish) world to rights when it is entirely within your power.
In governmental terms, it has to be borne in mind that some matters are "reserved matters" - i.e. under total control of WM - but that doesn't stop some from slating the SNP/Scottish Parliament over stuff not under their control.
Given the moves to strips away the power from devolved assemblies, the Scots would be wise to act quickly while they still can (& I'd go with an advisory referendum if Johnson won't oblige, sure its only advisory, what could go wrong). I find it amusing that the Scots are deemed unique, among small nations, in being incapable of managing their own affairs. Benevolent WM takes their tax revenue, gives a portion of it back, and calls it a subsidy..... some lads.....