For datadog, unfortunately there's no obvious altnernative despite many companies trying to take marketshare. This is to say, datadog both has second to none DX and a wide breadth of services.

Grafana Labs comes closest in terms of breadth but their DX is abysmal (I say this as a heavy grafana/prometheus user) Same comments about new relic though they have better dx than grafana. Chronosphere has some nice DX around prometheus based metrics but lack the full product suite. I could go on but essentially, all vendors either lack breadth, DX, or both.