Can't export H 264 in a Quicktime wrapper

you might try using mpegstreamclip and do a save as to convert an .mp4 to a quicktime with the h264 codec.  Used to work.  And they is to do a "save as."  Goes very quickly.  You're just changing the file wrapper...   Here's where to get it.

http://www.squared5.com/

Do not try and download from any other site.  I once told a client to get it, and he downloaded what he thought was the program and managed to install a relatively benign virus that mucked with his internet experience.  

You're right, there’s no longer an option to export Quicktime in H.264. A good workaround would be to use a plugin like AfterCodecs to do it. It also gives you more options during export and gives you the option to select a specific bitrate or filesize.

https://www.autokroma.com/blog/How-to-Export-H264_MOV

But you can do a lot more with AfterCodecs, it’s a very useful plugin for PP, AE and AME. It gives you all the codecs you might need - like ProRes 422 / 4444 / XQ, all 4 HAP codecs and many more - in .MP4 and .MOV containers. It also gives you the best and fastest compression for H264 / H265 with a lot of customization like the ability to render in 8K, FileSize targeting, custom Framerate, custom Resolutions and youTube profiles. Plus it has some cool features like MultiRender Markers to batch export clips in PP and the ability to export all Audio tracks separately.

Good luck

MP4 is the ubiquitous default for H.264 media.  You're better off using that.

The QuickTime option is gone and won't be coming back.

What you're trying to export to is (I believe) a 32-bit QuickTime 7-era format, which has been EOL'd by Apple. So all NLE companies (including Adobe) must eventually comply by eliminating support for such a format. The only supported codecs that are allowed in the QuickTime wrapper require full 64-bit support.