I've definitely had occasions where I was like "What did they just say?" because it was all garbled with the other sounds. It sometimes does give the impression that the "loudness war" that affected music production starting in the 90s is creeping into TV & film. For watching at home, the customer has a remote control with a volume button. If they want things loud, they can make it loud themselves. No sense in "brickwalling" the audio for things to be natively louder at a given volume level. Good sound mixing with a wide dynamic range is important.

I didn’t have a problem with Oppenheimer, but Dune with all that whispering made me quit the film.

I think it’s specifically that film series because I don’t find Villeneuve’s 2049 has that problem.

But I’ll say this, I find the issue more prominent with Netflix productions and postings than anything else… really quiet talking, really loud music and sound effects (not universally true, but I find Netflix; particularly in the pre-Coronavirus era, had terrible audio balance for home systems; but it seems to generally be a lot better nowadays).

One thing might be that I also got a new speaker system around that time and that might have banished the problem… however, not for Dune.

I think it is generally true that in older films they make a point to make all important dialogue clear; the unclear dialogue is generally more about the character’s emotional state than what they’re saying: Braveheart, for example.

Yes, Netflix had some issues with some of their shows in the past, they had way too wide of a dynamic range. Not so much anymore, though they are not exactly fully HDTV friendly either.

As I said, theatrical mixes are made for certain level (7 on Dolby scale, which is 85dBC per front speaker with -20dB RMS, measured with band limited pink noise). If you want them translated to home environment they need to go through lot of compression. The thing is, both Netflix and Amazon opted for wider dynamic range than what HDTV standard dictates - which is good for sound if you have actual home theater environment and you listen at high levels, but not so good for people who just want to "watch TV", like they used to. 

Basically, although we're still "watching TV", delivery method and standards are mixed up and differ, although it's all under TV umbrella. You still have lot of broadcast delivering HDTV specced content, but major streamers opted for wider dynamic range that is more suited for home theater environment, which brings problems that have been talked about here.

While HDTV/theatrical mixing and the trend for actors to mumble their dialog have already been mentioned, I think a lot of filmmakers nowadays deliberately have the audio mixes done so that viewers at home have to turn the volume way up in order to listen to the normal dialog, because it's a simple way of ensuring that sudden crashes, explosions, and soundtrack flourishes hit the viewer with a much greater impact than they would do otherwise.

Netflix specifically went from HDTV standard to current one in 2018, with Amazon doing it in 2019, explicitly to provide for more dynamic range. As I said, there is this dual nature of current TV watching - broadcast HDTV, that respects TV dynamics and intended environment (though not as tight as old SD standards), and streaming, that delivers to TV, but not really intended for classic TV listening.

As for filmmakers deliberately making dialogue soft...well, from my experience, sort of yes, but not quite - they just want that dynamic cinematic experience that sound in theater allows for, not understanding delivery medium of broadcast/streaming or flat out refusing to accept they're not working for actual cinema theaters. So in a sense, yes, there is sort of artistic problem as well, since some of them are behaving as if movies/shows they're making for home environment can have same aesthetics and approach as theatrical films (you can see this not only in sound, but picture grading as well) expecting for viewers to have home theaters to fully appreciate their "vision". 

When possible, opt for that.

No point in using surround sound as an option if you only have a soundbar, stereo speakers, or TV speakers. 

I'm a bit tight on space and don't want to buy a super cheap 5.1 setup, so I'm using a soundbar for my main TV. 

Yes! It is always a problem. The sound can be at a decent level when starting a new episode of a tv and then just rapture all eardrums in a one mile radius when the intro music starts.
And movies on the big screen also where they do not seem to care if the dialogue is distinguishable or not. For me what people say is the most important driving factor of a story and to not be able to hear it clearly just frustrates me. When watching at home my sound system can detect and amplify speech, a feature I have never turned off since I started using it.
And don't get me started on different music tracks on Spotify. I get that each track is its own artistic expression but I still dislike needing to shift my volume back and forth just to get -the same- sound level.

Meant to post this earlier but couldn't find it. Gemini was actually helpful!:

In terms of surround, I used to have floor speakers and what not. When sonos arc with era 300. Clean, easy to setup and sounds pretty damn good.

Yeah it's not only a mixing thing I suppose but also the trend of actors mumbling their lines in a lot of recent films rather than speaking clearly. Nolan and Villeneuve's films are notably guilty of this, much as I enjoy them, everyone talks in that really low "dramatic" half-whisper.