Joining & participating in forums like this one helps a little. There's a FaceBook page called Reinventing the Wheel - the Music Barn...
https://www.facebook.com/groups/483326849098435/
that is similar to the Showcase but requires one to listen & comment to three songs per one's own song posts. There are squillions of other songwriter forums each is, essentially, the same in that you listen & comment then others do likewise.
Many folk post songs on Spotify etc via mobs like Distrokid. I've not come across one that seems reasonable to me but, then again, I don't use paid streaming platforms.
YouTube is a great place to post songs because you can have a decent audio quality with a place holder, lyric or specially made video. It's a platform that is very popular. I get more listens through that looking glass than on the three listen/respond forums I am a member of combined. Though that's most often "through traffic" from me posting a link on FaceBook.
As Misha says: Fivvr is quite popular and quite good, by all accounts I've heard, and the synth voices are incredible these days.
As you know, I struggle to sing and am, slowly, learning to use tuning effectively & less obtrusively...no quick fix down that road.

Cheers
rayc
"What's so funny about peace, love & understanding?" - N.Lowe