>customer network behind this Meraki Network is not secure at all
No one can simply say they are "secure". And I certainly would not tell you that "you are not secure at all". Security is like temperature. There are a whole range of values.
You need to make a decision about what you feel is sufficient and go for that. You need to consider what your risks are, and put in sufficient mitigation within what you can afford to stop those threats.
Personally, I have only ever sold Advanced Security licences to customers. I personally consider the benefits of the content filtering to be able to block known malware sources and other things to be very valuable (proactively stop someone from even being able to download the malware rather than retrospectively trying to deal with it afterwards). And then their is the great IPS engine built around snort to try and stop attackers from using known compromises to take control of your computers - and lastly AMP - the ability to scan HTTP downloads for malware.