They have been using the same rocket for like 30 years. I'm not sure they are organizationally equipped to innovate anymore. Similar to the standard NASA contractors, who are rearranging shuttle parts to make the SLS and costing and order of magnitude more than even SpaceX's outlandish experiments from scratch.

Also its entirely possible the cost of a Soyuz launch is cheaper than a Falcon9 despite re-use, due to it being used for so long and slightly smaller.