As a teenager I kept up my attendance because I was in the church choir and loved the music opportunities and training that I had.
As a child, we chose our church because the Sunday School was during the service so my parents could engage in the morning mass and we could have age appropriate crafts and stories all in the same time and place, it was convenient.
Our church has lots of ways for community members who aren't practising Christians but do want to be involved in the heritage and care of the building and grounds for the community. So there's no pressure but a well attended and sociable gardening group who volunteer weekly, by coming into the church for tea and cake at the end they see the posters about events coming up and they also grow to feel more comfortable and welcome in what can be an imposing space.
In a similar vein, holding non church events in the space has brought in venue hire AND people who start to feel more at home in the space or hear about when services and other church connected community events and opportunities are on. Things like book talks from touring authors through a local bookshop. Music concerts (male voice choir, brass band, etc).
We had the opposite of a welcoming priest a decade or so ago and he did so much damage to the relationships and connections that his predecessors had built. He pushed away some really vital community treasure in people - the woman who led Sunday School, the woman who ran the midweek toddler group in the church hall (often a good connection for people new to the area to find out about Christmas tree festival, Easter family focused service, etc). It could be worth doing a bit of research into how people feel about the church - just a short google form or survey monkey circulated through local facebook groups.
A church close to where we live and our primary school promotes things like Messy Church and their Christingle service via the school newsletter, the vicar engages with the school about visits, occasional assemblies (it's not a faith school), and they have a youth club (for late primary/early high school) one evening a week that my son's gone to with his friend a few times - I think that only works with the right people involved but this one works well - again, as a kind of gateway community activity.
Music is huge, I know people have their own preferences but being clear about what's on offer is useful. When my grandma's church merged with another I think they had alternate weeks of more traditional hymns with the more lively band weeks - and people opted in and out of what they liked.
We've had a really well attended annual crib service - children are encouraged to come dressed up as any of the characters or animals from the nativity and they help to set up the crib scene. It's good for adults with young children who can't come to midnight mass, and people who are visiting their parents over the holidays often come en masse. Easy, well known Christmas songs work well, it's a lovely thing.
Midnight Mass is well attended as it's a big church in town, it comes immediately after a carols by candlelight concert - sometimes a soloist & organist, sometimes church choir & organist.
We have a community event in the church yard in the spring and early autumn which people like to come to as it's a chilled family friendly event, BBQ, bouncy castle, games, a few stalls inside the church, a local ballet school and community choir perform in the grounds too so we pull in their parents and families.
One event at a local church I loved to go to was with teddy bears zip lining down from the bell tower. You took your own cuddly toy, there was a form to fill in, volunteers dressed as nurses would do a health check on the bears, there was a stretcher that children would carry them on at the end. You paid per bear. There was different music played for each bear and a voiceover from the vicar with the name of each toy and an interesting fact about them. It was a hoot. Really odd and delightful and wholesome. There was a BBQ and soft & hot drinks available. A really lovely family friendly fundraiser. We found out about it from school.
I have friends who didn't attend church as children who have chosen to join churches with their own children as adults, partly because of faith but also because of the sense of community and welcome.
Warmth and friendliness are obviously helpful! And an understanding and accommodating approach.
A friend of mine lives very close to 2 churches in our town and attends one with her children who go to that church school. When she was planning her wedding she asked at their church and it was going to cost her an incredible amount of money (she just wanted to walk to the church, have the service with close family and a couple of friends then walk down the hill to the Italian restaurant where she worked for a meal, it was a low cost, low fuss, super local thing), she felt really upset and went to ask the other church where the vicar gave her a tour and when asked the cost sucked her teeth like a mechanic and said "oo, I'm afraid it will be about fifteen" "as in £1500?", "oh gosh no, just £15, I need to cover the costs of the extra candles, the rest of it's my job, that's what we're here for". And she switched churches for the wedding and Sunday services!
Community events in the church hall that have gone down well: quizzes, barn dance, wine tasting!