It's been a long time since I did tapered sliding dovetails.
When I did them I made a jig to use with the router with a guide bush and the slot in the jig was tapered, but very slightly, maybe 1/100". When I did the matching piece on the router table, I used the same bit set to a matching height of very slightly less and to account of the taper I put a piece or two of blue tape on one or both sides of lead end of the board.
Since I was routing both sides of the shelf the set up was a little fiddly but once you got, you're good to go.
The very slight taper was amazing. The pieces "fell" in about 90% of the way and a bump with your hand or a rubber mallet sent the home. They locked up, very had to get apart.
I had not considered using a steeper angle, thanks for the suggestion.
I often glued mine with epoxy because it acts like grease and has a long open time and does not swell the wood. A few I glued with Titebond swelled and were a sumbitch to drive home.
Now that I think about it, wonder how hard it would be to make them straight on one side and dovetail on the other?