Agree, building this in 2021 is not a good use of data engineering time.
As well as the SaaS packages like Amplitude and Mixpanel, you also have great open-source tools and platforms for mobile and product analytics like PostHog (https://posthog.com/), Countly (https://count.ly/) and Snowplow (https://snowplowanalytics.com/).
Disclosure: Snowplow co-founder.