I want to use it for spoken explainer video's. I tried out several machine generated audio tools, but generally it sounds, well like a machine.

Play.ht sounded interesting. There are a lot Dutch voices so I bought a code and tried it out. It is not so good as I hoped it to be, but it is usefull.
From the 14 voices, 12 sounded really artificial. Only two voices are usefull in my opinion: Ruben and Zoe. To make it more natural you can add effects like: "Natural breathing" and naration styles like "Regular", "News" and "Conversational". A pitty that Zoe doesn't have those options and Ruben only has the "Natural breathing" option. For a 30 second video I needed a text 56 words. You should listen/test carefully before you click on Convert. Each conversion (also same text in other voice) costs you a credit. Great to hear that Play.ht is considering changing the credit in this deal. Currently 5 credits (1 credit=2000 words). Heard that they change it into credits for 300 words. Or maybe a total montly word limit. Even beter for me.

To save credits you can prelisten. I add a return after each sentence which makes listening easier.

And currently you can't save text. So don't type it in there but make a text copy elsewhere. They told me they are working on this.

I didn't check voices in other languages so I'm only reviewing it for use in the Netherlands. Only two voices Ruben and Zoe are usefull. But to be honestly those voices are the best artificial voices in a tool that I encountered yet. You can hear that they are machine generated but it isn't as distracting as other voices. So they are quite usefull. Also considering that they are planning to change the credit system, makes it more interesting to use for explainer video's. I hope they are going to add more good Dutch voices and that they are going to add Naration Style and Auto breathing to those and hopefully at least for Zoe and Ruben.