At present in the UK, a shareholder in receipt of a dividend gets a tax credit to take account of the fact that the company paying the dividend has already had to pay corporation tax. If the shareholder's dividend income added to any other income is below the higher rate threshold, they pay no tax at all. If the shareholder pays 40% tax on their earned income, the tax credit means that the effective tax rate for the dividend is only 25%.
There's no double taxation for companies that distribute profit as dividends, it might look like it, but all that happens is an adjustment to the tax rate to take account of the personal circumstances of the person who receives the dividend.
Customers pay a sales tax, which the company collects on behalf of HMRC. The company doesn't pay it. No double taxation there either.
Companies only pay corporation tax on profits. Gross pay (i.e. salaries including income tax) is an allowable expense and therefore no double taxation there.
Corporation tax is _not_ double taxation, pure and simple.
If a company retains profits, they will (and should IMHO) pay tax on them. If they invest those profits in things that are useful to the country (like investing in capital equipment to develop the business) then there are further tax credits available.