I think that you can keep systems simple and HA if you forget about multi-master components and design active/passive solutions instead, whose behaviour in fail

I think that you can keep systems simple and HA if you forget about multi-master components and design active/passive solutions instead, whose behaviour in failure scenarios is much easier to understand and much less likely to go wrong, especially if you also forgo attempting to autorecover failed components after a failover event. If no HA is fine 90% of the time, simple HA is fine 99% of the time.