The BBC & the CBC produce a lot of dramatic radio with full casts & music & sound effects, but not all that much science fiction - see BBC Radio 4 Extra, for example. CBC’s Vanishing Point is the most recent dedicated speculative fiction show I’m aware of with that level of production values.

There have actually been a lot of really good independent audio dramas in recent years. To name just a few:

Edict Zero - A police procedural on a far flung colony planet.

Orphans - A group of people with no memory crash land on a mysterious planet where they're being hunted.

Archive 81 - Starts as a story about a guy investigating paranormal tapes, then eventually moves into more of a dark fantasy type setting.

Theater of Tomorrow: A SciFi anthology series, with some relatively long multi-part stories.

StarTripper!! - Lighthearted show about a desk clerk in the future who grows bored of his day job and buys a spaceship to travel around the galaxy.

Our Fair City - Set in a futuristic city standing alone in a post apocalyptic wasteland, it's a bit of a screwball comedy/drama dealing with the various residents who reside there.

MarsCorp - SciFi comedy about a woman who's been reassigned to assist the Martian colony effort and finds the entire project on the verge of collapse.

As you can probably tell, I tend to listen to shows in the SciFi/Fantasy genre. There's a lot out there, but I picked ones that are relatively well written (in my opinion) and give the feeling of a big production (full cast and sound effects).

Yes, but it's more novelty stuff. I know the Atlanta Radio Theater Company does it ( https://artc.org/) and of course, The Thrilling Adventure Hour ( http://thrillingadventurehour.com/ )

Mission to Zyxx, although a parody and not always great, has great sound effects and bits of score.

Lamplighter Theatre produces many quality classic and Christian-themed dramas, hosted by John Rhys Davies.

https://lamplighter.net/c/lamplighter-theatre/

here is a list of shows i have listened to so far:

Broken

Caalo Xan

Deep Vault

Earth Collective Story

Edict Zero

EOS 10

Escape Velocity

Exoplanetary

Falcon Banner

Foundation Series (BBC)

Girl In Space

In Darkness Vast

Leviathan Chronicles

Liberty

Nova Star Hunters

Our Fair City

Project Stellar

Ruby

Starship Iris

The Bridge

The Bright Sessions

The Fourth Ambit

The Kingery

The Orphans

Tides

Tin Can

Transmissions From Colony One

Vast Horizon

Wolf 359

if you like star trek, there is a list of fan audio drama here:

http://startrekreviewed.blogspot.com/2009/06/247.html

the Leviathan Chronicles is extremly well made. after years of hiatus currently the third season is airing.