There are a number of things a photojournalist can do to improve the appearance of images shot under such lighting conditions.

• It all starts with evaluating the lighting. If there are mixed light sources in the room that might be problematic, select a shooting position that allows one of the sources to be the dominant one. In the case of such high profile assignments as Congressional hearings, they often position themselves so that the continuous lights used by the video people in the press corp are their main source of illumination. Many facilities used for such meetings have broadcast quality lights built in.
• Lens selection. Fast zooms or even fast primes are the bread and butter for covering such an event.
• Intended usage. Most such images are going to be published in fairly low-fi settings. Newsprint is very low quality image reproduction. Web distribution at typical sizes isn't much more demanding. Neither is usage in a news magazine. Photojournalists realize that images can look acceptable in print and online without having to be anywhere near as high quality as a large gallery print.
• Use the right tools. I know many full-time PJs who are not afraid to push ISO to 6400 and beyond when they need to. The flagship pro bodies are optimized for this. They tend to be lower resolution than other "studio", "landscape", or even "sports" bodies offered by the same manufacturers. The Canon 1D X Mark II is only 20.2 MP compared to the Canon 5DS that is 50+ MP. The Nikon D5 is only 20.8 MP compared to the Nikon D850 that is 45.7 MP. Larger pixel pitch means better light gathering capability and better high ISO/low noise performance.
• Repetition. It's probably pretty rare for an event like Congressional hearings to be covered by a newbie who has not shot in the same room before. Sure, everyone has to shoot a specific room for the first time at some point, but many of the PJs that cover things in DC have been there for years if not decades covering such meetings on a daily basis. The more often one shoots in the same environment, the more one can refine both their technique and in-camera settings with regard to not only ISO, Tv, and Av but also with respect to contrast, saturation, color temperature and WB correction, etc. (I do it with sports venues I frequent all of the time. I have a little "cheat sheet" in my bag with manual exposure settings as well as CT and WB corrections settings for various venues in which I shoot. If I need to move a jpeg quickly the images look much better than just setting WB to "auto". If I have time to process a raw image all the better - I can review the images with the color already very close and then batch apply Hue/Saturation/Luminance adjustments in addition to the CT/WB settings already applied in camera.)