Well, this was compensated right at this time in the 2nd half of the century starting with the measurement of the Lamb shift, which triggered the entire development of the 2nd period of QFT. The first period was already very early in the "Dreimännerarbeit", where Jordan already quantized the em. field in addition to the electrons, but at that time the idea was not appreciated, because some eminent physicist thought that was "too much", and indeed it's well known that you get very far without quantizing the em. field; at the time the only thing not explained was the necessity of spontaneous emission to kinetically derive the Planck radiation law a la Einstein 1917). The 1st and 2nd period of the QFT development is most comprehensively described in Schweber, QED and the Men who made it (though this book is full of unfortunate typos in the formulae :-().
The reason, why there's not so much after 1970 may be that the last breakthrough in the foundations was Bell's work in the mid 60ies, which has of course then lead to a complete new field, which I'd call "quantum informatics", which is of coarse closely related to quantum optics, but that are applications of QT, which has been more or less settled in its foundations already around 1925-1927.
Also the Standard Model was completely formulated around this time. I'd say the last fundamental building block was 't Hooft and Veltman's proof of the renormalizability of Higgsed and un-Higgsed gauge theories (1971) as well as Asymptotic Freedom (Gross, Wilczek, Politzer) of non-Abelian gauge theories and the establishment of QCD as the description of the strong interaction.
