Tomorrow the Scottish Parliament will vote to set income tax rates and bands for the first time.

This has unleashed the usual hyperbole, with Alex Rowley, Scottish Labour’s deputy leader, predicting that Holyrood will “enter the history books” as a consequence.

And if Labour has its way – which it won’t – then Scotland will add a penny to the basic rate of income tax and create a 50p top rate for “the richest 1 per cent”. This, it claims, would “stop the cuts”.

This, however, is modest stuff, although the SNP’s fiscal proposals are more modest still, chiefly no increase to the threshold (as in the rest of the UK) for the upper rate and no 50p rate. The result? Some Scots will pay an extra few hundred pounds a year in tax.

As Finance Secretary Derek Mackay has admitted, this move is largely symbolic, for although it will raise some additional revenue, it isn’t really necessary for the Scottish Government to meet its spending commitments. Again, far from heralding a bold new dawn, the newly-devolved powers have brought forth a damp squib.

It wasn’t supposed to be this way. I remember back in the late 1990s there was a general expectation that tax-varying powers meant the new Scottish Parliament would be the real deal, a devolved legislature with teeth. But in reality the old Scottish Variable Rate proved more theoretical than real, with none of the major parties showing any interest in its use.

Later, the Calman process, which proposed giving MSPs control over 10p in each income tax band, fuelled a growing consensus that in order for the Scottish Parliament to become more “responsible”, it needed to be able to raise revenue as well as spend it.

Tomorrow that argument reaches its logical conclusion with Holyrood voting on a “Scottish Rate Resolution”. But, in truth, things haven’t really moved on much beyond 1999: the Scottish Tories have reverted to railing against the “Tartan Tax” while the SNP, having long demanded this particular fiscal lever, are strangely reluctant to pull it.

So far from becoming more “responsible”, Holyrood remains terrified of behaving like a grown-up parliament. Why? Largely because the Thatcher-era consensus still holds that income tax should either stay the same or go down. Stealth tax rises are fine – just look at the SNP’s approach to business rates – but woe betide anyone who tries to vary the basic rate of income tax, for voters won’t be happy, especially come election time.

In truth, Scottish Labour has only belatedly shown any interest in bucking this orthodoxy because it’s now so politically weak that it knows full well it won’t be in a position to make it a reality, while the SNP, conscious that the Smith Commission was something of a Unionist “trap”, has come up with a tax increase that isn’t really a tax increase.

With the Nationalists, the usual conceit holds. Sure, runs the spin, the First Minister would love to be more redistributionist and tax the rich a bit more, but a) they might leave the country and b) the time to be bold is when Scotland is fully independent.

This, however, doesn’t hold much water. Last week Scottish Government figures revealed that the richest 1 per cent in Scotland possessed more wealth than the bottom 50 per cent. Furthermore, the gap between rich and poor is actually increasing, with the poorest 40 per cent of homes 9.4 times worse off in 2012/14 than the top 10 per cent, compared with 8.8 times in 2010/12.

Of course there are forces at work well beyond the Scottish Government’s devolved control, but such figures imply that the symbolic progressivism of free tuition, council tax freezes and free prescriptions have benefitted Middle Scotland to a greater extent than those arguably most in need. Yes, I know I’ve made this point before, but it stands repeating because it’s so obviously at odds with the SNP’s stated aims.

Most striking was the response from Equalities Secretary Angela Constance. The Scottish Government, she told a newspaper, was “passionate” about creating a “fairer and more equal Scotland”. So passionate, indeed, that it hasn’t really done anything to achieve that after nearly a decade in power, with ever-increasing autonomy and a (modestly) increasing block grant.

But these days, “passion” and good intentions appear to count for more than boring old statistics (or indeed results). Nor is it credible to suggest that the SNP will suddenly become all radical following a Yes vote, for a newly independent Scotland would have to prioritise fiscal credibility over reducing inequality.

Beyond income tax, meanwhile, the SNP’s fiscal worldview remains rather confused. Its big economic idea remains tax “incentives” – otherwise known as cuts – as applied to Air Passenger Duty and Corporation Tax, although the current First Minister is less inclined to shout the latter than her predecessor. Scottish Labour now attacks these things, having once more or less supported them, while the Conservatives opportunistically bang on about Scotland being the highest-taxed portion of the UK.

In a parallel universe, where politicians actually govern rather than posture, one might hope that some thought would be given to a more holistic overhaul of Scotland’s fiscal framework (which is arguably even more necessary if independence is to become a reality). To their credit, the Scottish Greens did actually do some of the heavy lifting on this front at the last election, although Patrick Harvie’s recent handling of the budget negotiations has rather overshadowed that.

The details, however, are still worth taking seriously. In short, the current basic rate of 20 per cent would be replaced with two bands, 18 per cent for the first £7,500 of income above the personal allowance and 22 per cent for that above £19,000. This would mean anyone earning less than £26,500 (which is, after all, most Scots) would be better off; income above £43,000, meanwhile, would be taxed at 43 per cent, and that above £150,000 at 60 per cent, which was the upper rate of income tax as recently as 1988.

The Scottish Greens calculate that moving to such a system would raise an additional £331 million which, if targeted correctly, would help reduce inequality, certainly much more so than the Scottish Government’s current plans. Now that would be much more deserving of superlatives like “historic” than what’s likely to transpire at Holyrood tomorrow afternoon.