I don't think promoting the idea of not needing to apply in advance of a discount is remotely the same as giving everybody a discount. There will still be criteria, like being aged 16-30 for example, so it will still be targetted.
Some railcards already have peak restrictions, no need for that to change.
Why give someone a free discount. Make people pay up front for one. Plus the targeted nature of railcards is the problem. Everyone should have the opportunity of buying a discount, as is the case in sensible countries.
You could do this already with a checkbox for UK citizen or not; though worth noting the current system of Railcards is already open to tourists anyway so again, no need for change per se.
I'm not sure means-testing rail fares is desirable nor do I think the cost of administering such a means-testing system (with or without an actual card) would generate a surplus. For starters the UK doesn't even track wealth, only income, so we wouldn't be taxing the wealthy more, many of whom actually pay low levels of income tax. A lot of means-testing schemes don't save the money it costs to administer. It may do for rail, but I wouldn't be so sure. If we were to adopt it though, yes we'd need an individual card for everybody (or everybody who wants a non-wealth discount) for that.
Neither of which I'm suggesting. A tourist would have the same opportunity to buy a national railcard - but likely find it not worth it.
Knowing that the wealthy might not bother with a railcard is not the same as means-testing for it - Although a means tested railcard is probably no more outlandish than any of the eligibilities we have now. Probably less regressive than some.