It really depends a little bit on what you need and what you exactly mean with 'scenery'.
The last version of vue I really know was 6 infinite, and that I used quiet a lot. Stable it was, but renders took forever even on fast machines and with much smaller resolutions than are needed today (I remember an update that crashed the disk with it's installer. Stupidly I had forgotten that when I changed the computer and had kept the updater ... (only this time without a save as I was just installing and installing ...)). So, I have mixed feelings about vue
. But for fast backgrounds with clouds and plants I still haven't found anything better for a halfway reasonable price. They were bought one or two years ago and try now to be again a solution for professionals (somewhere on the way since 6 they seemed to care more for the poser market than anything else).(Only the 'creator' solution is not bank breaking). But I still would try out the test version, just to have something for comparison.
Then there is terragen, meanwhile not even very pricey anymore. I never bought it, only had a beta version of 4, and have to admit, I never was that happy with it. Clouds have in my opinion almost always a slightly unnatural look, like painted (but I have seen a few pictures with good results). It comes with some plant library. There is a free version (with ridiculous low render settings) you could test out. With $ 349 (creator) / $ 699 (professional) it's cheaper than vue. To get good results you'd need some time to learn it (more than I ever invested), but it can deliver professional results. Certainly worth a look.
Then there is still carrara pro 8.5 around, which has something like a plant creator and volumetric clouds. It's sold from DAZ, meaning that there wasn't an update for eons. Two years ago I got it for free and have to admit, I'm a little bit surprised that they do sell it again for some 150 $ (it's from 2014). The quality is probably better then Bryce, as it's a thad newer. But it's quiet low in my opinion and I do mention it just because you could stumble on it on your search in the net... Definitely not worth that money imho.
World machine 2 is specialized in landscapes, which means it probably doesn't meet your needs, like everything else I know off can just do one or the other (like a ton of small programs that can create plants. If you find something for free working on a mac, let me know, please). All major 3d software has some built in volumetric objects with which you can produce smoke, clouds and stuff, very often just as a pricey plugin. And you can get a lot of plants, stones etc. from different sites (like xfrog). Some models you'll find for free (with instancing that part of the scenery can very well be achieved inside Cheetah).
And there is of course Houdini, which is a full grown 3d package that has an inbuilt terrain generator. It's widely (and professionally) used for fx, with everything you'd need for fire, clouds, smoke. But it's quiet a bit more than you asked for. It's not quiet bank breaking but nowadays only available as rented software with annual payment ... For non-commercial projects is a free version available (with a big fat watermark in the lowest part of the render (you can cut it away)).
And (now think of me as looking very sourly) blender, which probably has all the things you need, at least with some plugins (not all are free, though). Again a bit more than a simple landscape generator.