With regards to building better QEs or better Rs what has to be remembered is that Britain was in an Dreadnought race with Germany
That's true. In 1913 there was planned to be 4 ships built with 3 following in 1914. These were the ships that the designs U1-U5 and a few others of different letter codes were prepared for. Then the Germans passed the 1912 Naval Law. Though ostensibly the naval race ended in 1912, the Naval law of 1912 has several clauses that would concern the British. For starters it allowed them to dispose of the 4 BB's, 4 Large Cruisers and 4 small cruisers of their material reserve early. The immediate effect of which was that 3 BB's and 2 small cruisers to be added to the German Building Program. This law also allowed for an increase in active service personnel. This would allow the Germans to maintain 3 battle squadrons in full commission instead of 2.
In addition, by 1912 Italy had Dante Alighieri almost complete, 3 Conte de Cavour's launched, 2 Andrea Doria's in construction. Austria also had 2 Tegetthoff class in commission and 2 more under construction, with planning for the 4 Ersatz Monarch class already underway. The British had to plan around the idea that both nations may be supporting Germany in the Med and France may not be able to ensure control of the area.
This led to the 1913 building program to increase to 5 ships and 1914 to increase to 4, but the money for the naval estimates would likely have already been agreed with the Treasury. So the Admiralty had to try and get more ships out of the same money. This led to the U1 design being dropped and what became the R class ending up in service.
So what Britain did is probably the correct thing build something that is good enough now and build something better later which is how they approached every class all the way back to Dreadnought (which could have been an X4 fast BB design).
Though the Admiralty can generally be said to be a reasonable actor it is, I think, also important to understand that it was not a single actor. There were divisions and groups and differing opinions among those in charge of the Admiralty and not all of those viewpoints are equally valid. I do not think that it is a slander against the work of the Admiralty to examine the feasibility of some of the ideals put forward at the time and consider what it was that made them go a different way. I find that though many decisions have a very good reason for them some of them come down to poor relations between groups as much as to reasonable action.