That's not an accurate representation of the service at all. I'd say it's a lot closer to, say, New York City's subway service: something people love to hate, but that is, despite some flaws, quite successful, especially in comparison. The trains being full, literally, littoraly (to the coasts), or figuratively also calls to mind Woody Allen: "Nobody goes there anymore–it's too crowded".
All trains, even regional ones, also have heating and cooling. And while Acs tends to be underpowered and is broken more often than it should be, I don't remember heating, which is much simpler anyway, to have similar problems.
" I don't remember heating, which is much simpler anyway, to have similar problems."
On the contrary, it is way too warm in the trains in winter and badly vented. And you cannot change anything about it, because for safety reasons it is no longer possible to open a window even a tiny little bit.
All trains, even regional ones, also have heating and cooling. And while Acs tends to be underpowered and is broken more often than it should be, I don't remember heating, which is much simpler anyway, to have similar problems.