(1) Most tourists visit largely London and its near surroundings. Public transport in (and to) London is generally much better than other parts of the country.
(2) A lot of the downsides don't manifest if you're a relatively infrequent user and you're largely travelling at off-peak times. As a UK resident who doesn't commute on the railway, this also includes me -- my experience of trains is generally good because I travel at quieter times and I don't travel so often that unreliability is a regular experience.
(3) If you ignore the costs (by not being a taxpayer or because you're less price sensitive for infrequent travel and especially for holiday travel), then you're ignoring the large part of the argument which is "this privatization had massive inefficiencies and costs".
FWIW, the UK government pays about half of the 25 billion/year cost of the "operational rail industry" (source: https://dataportal.orr.gov.uk/statistics/finance/rail-indust...). I couldn't find the equivalent stats for Portugal with a quick search, so I don't know how that compares.