As you know most church music teams are all volunteer. It just depends on the approach of the worship leader and the leadership as to how particular they want to be about proficiency. Some churches will hold the line and not allow someone who is not especially gifted musically to play, believing that even if all they have is a piano and a drummer that can play it will at least sound good and be recognizable. Other churches take the "well if he wants to play, we should let him play" approach. Being a part of the latter can be extremely frustrating to a musician who wants to sound good.
I have played bass in church for quite a while. A few years ago I switched churches and after a while offered to playin the worship band. I was glad to see that they required an audition and I thought that because of that the situation should be pretty decent. Sunday morning playing sounded ok. Not great but had potential.
When I got to the audition I brought both my acoustic guitar and my bass. I was asked to sing a song as part of the audition, so I just decided to play my guitar with it rather than without. After I did that I put the guitar down and started to get my bass when she said," Oh...that's OK. If you can play guitar then you can play bass."
I almost walked out right there.
I decided to give it a chance.
it drives me crazy that rehearsals are so unprepared, and I have tried to effect change but no dice. At times I really want to step back from it but here is why I do not. And this is just me but maybe it will help you to possibly see it in another light. Maybe not.

When I decided to join the worship team I asked God to make me a servant and use whatever I could offer for the benefit of others and not myself. He took me up on it and is really trying to teach me how much it ain't about me. I play in two bands outside of church and I do it purely for my own enjoyment. The practice is for me to get better, the money I spend on gear is for me, the feeling I get when the band is locked in and rockin is for me. So I am pretty good at taking care of me.
At church rehearsals I have had the opportunity to help a few others realize the importance of at home practice. Gently and over time but the other bass player in the rotation, who never practiced at all now does so and is happy with his achievements and when he plays the band sounds a little better now. We have a guitar player who has also played out for years and is very good. He is now running rehearsals which is a big step in a good direction. Our worship leader is a singer, not a musician and doesn't focus much on the music. I think it is this way for a lot of churches.
Our sound guy is "still learning" and sometimes my bass isn't even in the mix out front. We use in ears and the bass is there ok. So I am there to provide a little low end bass groove for whoever is listening to me through their in ear monitors. I have decided that I am ok with that. I hope it gets better and I think that it will at some point as we progress but for now it's lesson time for me.
My wife, who loves to sing in church from the pew she is standing at, doesn't understand what I complain about because to her the music sounds great. And I look into the congregation as we play the songs they are singing to and I see happiness and not a care about what we sound like.
Anyway, I hope this helps.