You can use whatever system you want (syslog can drop the logs in a single box, no need for horrible tail-based concoctions), as long as you mantain it and it's

You can use whatever system you want (syslog can drop the logs in a single box, no need for horrible tail-based concoctions), as long as you mantain it and it's not Ops responsibility to fix your AWK scripts that look for events in logs from 3 different services for the same request and the same customer (and/or respond to the alerts those script generate at 2am after Bob forgot to update it to parse correctly a new log message - we have our own fires to fight already). I'm not saying one should go straight to ELK. There are other ways, but at the end of the day you are going to implement a similar stack, guaranteed, and you are going to regret using freeform logging instead of a sensible structured format.