VPNs are awesome in many different ways and we all use them today. But it is also important to know the limitations of VPNs that we use. A tool is only good when you are aware of its features and its limitations.
While VPN does hides your IP address, it is not a service that can hide you completely and make your perfectly anonymous. That is many users often overlook. Even the best VPN services might not be able to guarantee complete anonymity. Other than that while a VPN would help protection against most DNS attacks but still an old web page that is made to look like a legit website and thus tricking you entering your data can still work. While most phishing attacks can be blocked today by browsers and VPN but still a large number of people get hit by such attacks and hence can't be ignored. In such a situation you would have to use your common sense. You would have to look carefully at the URL and check if they are HTTPS websites or not
Other than that some VPN also claim to guard against malware. Obviously it is a great feature but it is not as good as security offered by to antivirus software. In fact VPN are not even close. So this feature of blocking malware can be used to complement but can not replace an antivirus.
Another important that should be noted is that security conscious organizations like banks might get confused by use of VPN. If you try to login your online banking account from a VPN connection then that might trigger alert for the bank and it can raise red flag on your account. It might think some hacker is trying to access your account and can even block your account to save it from potential threat. Obviously this is something that you might not like. You might also see more frequent captchas while using VPN. This is because of the same reason that your use of VPN can confuse different websites who are extra careful about their security and this obviously includes banks too.