Open Street Map. If something isn't accurate, you just update it like Wikipedia. I made some updates to my city, and now it works flawlessly

I use the app's by local transit services and organisations (9292, NS) and so far that's working out pretty well.

They don't have the reminder to indicate when your stop is coming up, but the last two or three times I tried to use that with Google Maps it just didn't warn me, so I don't think I'm missing out on much.

There are a bunch of open source transit apps as well, but little work as well as Google does when it comes to planning trips and finding alternatives. Sometimes there just isn't any open data about public transit and only a few shitty commercial apps have up to date information, but you could always check Google if the routes they suggest seem inefficient or too good to be true.

I almost exclusively use the app called Transit. It uses OSM data and shows live tracking for buses and trains (at least it does in my city). It's good for figuring other options like walking, cycling, bike share.

Try the Transit app, by Transit,inc..

It's a lot better than anything out there, as long as your area is supported.

Citymapper is the gold standard. Osmand is excellent, except for delays. Many countries have third party top-tier apps for transit and train navigation -- Trainline comes to mind in the UK, but it varies by region.