I'm a big fan of Firebase. The local emulators make working with it really productive since you can iterate locally against the full stack very quickly. SSO and auth are easy to use; way easier than Cognito. For most clients, it will be virtually free to operate until they reach significant traffic. For your static front-ends, Firebase hosting is fully integrated into Google Cloud CDN with no extra setup. You can extend it to full Google Cloud if you need to (e.g. connect endpoints to Cloud Run if you have container workloads). The Firebase Functions integration is really, really nice and allows for strongly typed invocations if you are using TypeScript. Real time with Firestore is easy and, again, free for most small customers. You can use any FE engine with it - React, Vue, vanilla. The Web Frameworks integration with Functions lets you deploy dynamic backends as well into Cloud Functions.
If I need SEO, I'll build using a framework like Nuxt.js or Astro.js and statically generate the output and host in Firebase Hosting. If I don't need SEO, I'll build regular SPAs using React or Vue.
The overall DX is really good compared to Amplify (closest alternative).
Supabase is also promising if you want to work with a relational DB.