Retailers aren't taxed any differently than any other business, so I don't think we can blame "crippling" tax regimes. It's also worth nothing that, assuming govt doesn't change it, that corporation tax is set to fall until 2020.
Online retailers have access to tax loopholes that brick and mortar retailers may not, however.
Unfortunately for high street retailers the way we shop is evolving and they can't keep up without radical change or a USP sufficiently attractive to keep them going (like Primark).
People have less disposable income and are spending less.
There is more access to a greater variety of brands and price points via the internet. Not that long ago your only options would have been whatever was in town, now the only limit is your budgets.
People are shopping more sustainably.
Business rates have risen as councils, squeezed by central government, try to raise money where they can. Rents have also been steadily increasing across the board.