@geovagriffith
I'm sorry that you feel offended by my wording, which was certainly not directed at you. However, I regret to say that it was a paraphrase of an attitude that I have encountered here time and again over the years (and which some Germans also cultivate when they go abroad).
To the point: It is indeed not a good idea to buy a first-class ticket for a regional train where you cannot reserve a seat and which only has a very small number of first-class seats. First class is often empty on suburban trains, but less so on regional express trains which are set up by the federal states as a replacement for long-distance trains that DB simply no longer operates. As for the ALEX mentioned above, its few first-class compartments are always well filled with passengers traveling from Prague to Munich during the travel season, so personally, I would consider the risk of having to stand in first class when boarding in Regensburg to be too great.
Also, sad that the German rail system has deteriorated since we lived there over 30 years ago.
It's actually not that simple, or rather, it's a paradox: the decline of the railways is due in no small part to it's improvement, i.e. the excessive expansion of local train traffic. Here in the Augsburg area, we nowadays have at least three times as many local trains as we did thirty years ago, and that's on the same rail network. The reason for this is that responsibility for regional transport has been transferred from the DB to the federal states, which, under political pressure, always order as many trains as they can just about afford. According to a recent study by the University of Stuttgart, overcrowding and management errors at DB (where the majority of people now come from outside the railway industry) are a much more important cause of poor operational quality than damage to the rail network, which is "only" responsible for 15% of delays. The fact that problems with the network are so strongly emphasized is due to the press work of DB, which has a great interest in presenting things in this way. This is because when a line needs to be renovated, the federal government pays, whereas normal maintenance has to be paid for by DB itself.
I'm sorry you had to stand so much on the train. But I think the steady increase in the price of the Deutschlandticket, which is to be expected, will ensure that the situation eases.