Most of the complexity in observability is clientside.
It is not hard to spin up Grafana and VictoriaMetrics (and now VictoriaLogs) and keep them running. It is not hard to build a Grafana dashboard that correlates data across both metrics and logs sources, and alerting functionality is pretty good now.
The "heavy lift" is instrumenting your applications and infrastructure to provide valuable metrics and logs without exceeding a performance budget. I'm skeptical that Datadog actually does much of that heavy-lifting and that they are actually worth the money. You can probably save 10x with same/better outcomes by paying for managed Grafana + managed DBs and a couple FTEs as observability experts.
You could hire 100 people to manage your timeseries data and save 70%
I used to be quite fond of Datadog but after one or two completely surprising bills (thanks to their granular but unintuitive pricing model), I wouldn't recommend it to anybody any more. If I were more cynical I would say the pricing model is designed to be confusing so customers spend more than they need, and this is only made worse by the extreme breadth of the platform now.
These days I'd suggest to just suck it up, spin up a Grafana box, and wire up OpenTelemetry.