I think there is a lot to be said about the technology factor to it. On the movie side special effects heavy stuff is still largely the wall-to-wall green or blue screen sound stages. Motion capture and motion tracking tools have all got insanely good so studios can do a lot more than say in the days of Lucas' Star Wars prequels (which were notorious wall-to-wall green screen films of their era), but also the budgets and time constraints and "crunch" still provide a lot of barriers to how well the digital/analog integration is and the overall look of all the effects. Also, there's only so many ways to light a green or blue soundstage so that things are readable and you don't get extra ugly color spill that the special effects have to work even harder to remove. (I think the base lighting options being so mostly homogeneous is a subtle but huge factor in the overall things always feeling that way. Differences in lighting have always been one of the biggest "cinematic languages".)
Special Effects houses working on those sorts of movies are probably using heavier, slower renderers than Unreal Engine today, but given the average life span of an effects house is still appallingly close to 2 years and scenes scattered across 1.5 movies, those renderers are still generally off-the-shelf or borrowed from other companies. Industrial Light and Magic is about the only effects house that no one wants to kill, so also becomes something of a homogenizing factor in whatever tools it white labels for sale/rents to other effects houses. Disney owning ILM seems to be like an obvious factor that almost everyone working on an MCU film is trying to rent or ape the ILM house style at all times.
It's also interesting that right now TV can't afford as much time with the motion tracking/motion capture tools and studio spaces of wall-to-wall green screen, so in the effects heavy shows we're seeing a lot more experimentation, some of which I'd argue look better than the movies currently. For big instances, right now ILM's TV efforts with The Volume (and CBS Paramount's copycat AR Wall and other studios have copycats now too) are fast changing the look of TV. Because these LED walls are their own light source which dynamically reflects what the background should be doing it seems like there's a ton more options for lighting scenes in these rooms/volumes/spaces or doing shots that would be tricky or expensive even with how great motion tracking and motion capture have gotten. Of course the trade-off there is that the real-time background rendering requires a rendering engine more in the vein of Unreal Engine, and allegedly in most cases is definitely Unreal Engine, so "default unreal engine look" starts to apply literally to background elements in TV shows.
It's not just CGI, background replacement and other effects work. Some cinematographers have been noting that the increasingly flat, uninspiring look of much modern content is partly due to the amazing dynamic range of modern camera imagers as well as HDR production workflows. While wonderful, this also enables a kind of laziness (or expediency) when shooting. You don't have to specially light many scenes as much (or at all) as long as there's enough ambient light. While this can enable styles like cinema verite to be higher-quality, it also lets film-makers just go with ensuring there's enough flat light overall and call it good enough. Intentional lighting is hard and time-consuming but it's also one of the most expressive visual elements of film-making.
Another factor is that dramatic lighting tends to dance closer to the edge in terms of quality. Lighting a high contrast scene with inky blacks in one area and your hero elements in moody shadow means that those very dark areas are at risk of slipping into the floor of imager noise. The same is true when there are extremely bright elements near the upper-bound of clipping. While modern imagers and HDR capture give film-makers more latitude than ever to avoid these problems, perversely, the same luxuries seem to be making younger film-makers less skilled, or at least less confident, in their ability to dance close to the edges of too dark or too bright.
Newer post-production color grading tools also enable new degrees of what's possible to "just fix in post." Once again, this is wonderful when we need to fix a mistake or for amateur and hobby productions which don't have the time, budget, gear or even knowledge to do creative lighting. The downside is it creates an ever-present temptation when under time and/or budget pressure to take the shortcut and just bounce a key light off the ceiling and a fill off the wall and call it done. It's sad because modern imager sensitivity and battery-powered, micro-sized lighting instruments now make it easier, cheaper and faster than ever to do intentional lighting at a Vittorio Storaro level. Storaro might spend half a day with a crew of six gaffers lighting one scene that a four person indie crew could largely recreate today in an hour with $1k of lights, clamps and stands from Amazon.
Special Effects houses working on those sorts of movies are probably using heavier, slower renderers than Unreal Engine today, but given the average life span of an effects house is still appallingly close to 2 years and scenes scattered across 1.5 movies, those renderers are still generally off-the-shelf or borrowed from other companies. Industrial Light and Magic is about the only effects house that no one wants to kill, so also becomes something of a homogenizing factor in whatever tools it white labels for sale/rents to other effects houses. Disney owning ILM seems to be like an obvious factor that almost everyone working on an MCU film is trying to rent or ape the ILM house style at all times.
It's also interesting that right now TV can't afford as much time with the motion tracking/motion capture tools and studio spaces of wall-to-wall green screen, so in the effects heavy shows we're seeing a lot more experimentation, some of which I'd argue look better than the movies currently. For big instances, right now ILM's TV efforts with The Volume (and CBS Paramount's copycat AR Wall and other studios have copycats now too) are fast changing the look of TV. Because these LED walls are their own light source which dynamically reflects what the background should be doing it seems like there's a ton more options for lighting scenes in these rooms/volumes/spaces or doing shots that would be tricky or expensive even with how great motion tracking and motion capture have gotten. Of course the trade-off there is that the real-time background rendering requires a rendering engine more in the vein of Unreal Engine, and allegedly in most cases is definitely Unreal Engine, so "default unreal engine look" starts to apply literally to background elements in TV shows.