The R&D of new equipment is a necessary part in wartime economies. The application into mass production and the proper utilization of this equipment is at least as important, too.
However, the one aspect does not necessarely prevent the other from working, nor can it be viewed seperately.
R&D is a capacity which can be used or neglected, it does not PER SE cost that much ressources compared to mass production fundings.
For example: In 1940, Hitler suspended all long time R&D not because they haven´t been useful in this war but in order to simplify mass production, exactly what You have in mind. This can be seen as a very questional ratio. It indeed turned out to be counter productive as soon as the wehrmacht faced the KV-1, KV-2 and T-34 in the East. In this timeframe, Germany LACKED in R&D. I could also take examples from Radar technologies or powerplant technology. The Fw-190 nearly was cancelled because of this! The suspended R&D left Germany in 1940-1941 with rapidly aging equipment in mass production.
Another aspect is mass production itselfe. The capacity of mass production is widely dependant on the potential economy, organization, ressources and the level of basic tooling technology. The potential economy was excellent in Germany, organization was at best mediocre until 1943, when Albert Speer overtook the ministry of arms and industry, ressource avaiability was acceptable until 1943 (a cross trade effect with the higher productivity caused by Speer and the generally strong dependance in raw materials) and the degree of basic tooling technology finally improved in incremental steps over the years.
What now happens if You combine these aspects and analyse them in relation to time is clear:
1.) Germany could afford long time R&D (short time R&D usually aims at the improvement of existing equipment) in the early war period but suspended most of them (only finalizing projects such as the Me-163, Me-262, He-177, He-280, Ju-288 and Fw-190 were continued) in 1940 in order to simplify mass production. The production numbers still did not increase substantially in this period thanks to a low basic tooling level, weak organization of production / distribution of ressources.
As a result of this a number of the remaining projects were reduced in importance (Me-163, Me-262) and even cancelled in 1941-42, such as the complete bomber-B program (which left Germany with no advanced medium bomber in the mid war period).
In the developed mid war period, things were reconsidered. Albert Speer overtook the organization, he dispersed industries, established a self sustaining transportation network and improved the basic tooling level. In the meantime, R&D of specific projects rapidly expanded, resulting in the Tiger and Panther designs (both beeing applied to quickly into mass production), the V-1 , certain advances in rocketry and jet engeneering.
In this period (1943-wars end), the production numbers increased drastically despite the expendad R&D! R&D was used in it´s full capacity.
The late war period showed an excessive use of R&D for desperate projects (death rays, sun guns, the V-3, Natter), which perhaps prevented funding of more groundstanding projects. In the meantime mass production of the latest early war projects (Me-163, Me-262) began to be applied effectively. The production numbers still show a growth at wars end but since Germany only improved organization and tooling level but not the potential economy nor it´s raw material sources, it must ultimately show critical shortcomings in this timeframe.
What if the long time R&D had been suspended completely? With hindsight we are able to estimate that neither the Panther, nor the Tiger I or -II, the Me-163, the Me-262 or the Ar-234 would ever see the battlefield but instead the Pz-III and Pz-IV, the Me-109, Ju-87, Ju-88 and He-111 would still be used on the battlefield in excessive numbers. Even if we assume two times the actual production of 1942, it would not have made a difference in the East and arguably the wehrmacht would find itselfe in deep troubles from late 1943 on in the West and totally outdated from mid 44 onwards in both theatres.
It even might happen that Speer don´t overtake the ministry as this post was dependant on the rapid application of new R&D into mass production, which would leave Germany with less production AND less R&D.