When you buy an different router with hardware support you can use IKEv2 which is safe, L2TP is not
For this purpose it does not really matter if the VPN is "safe"...
Traditionally VPN was used to inter-connect two isolated networks (e.g. subsidiary local area networks) over a public network, and it was important to make sure that someone who could capture packets on the public network would not be able to look into the transported packets, insert new packets into the stream to attack systems on the isolated networks, etc.
Hence the use of authentication and encryption.
However, today most people (including the starter of this topic) use VPN in a slightly different meaning: to transport all their traffic that is to be sent to/from the public network to another place where it will then be released onto the public network.
They can do that for a couple of reasons:
- because their local connection is unsafe and can be tapped by bystanders (e.g. public WiFi)
- because their ISP is somehow modifying the traffic in a way they don't desire (e.g. interception of DNS requests and insertion of own code into http traffic)
- because they do not want to associate their traffic exit-point with themselves
- because they want to have their traffic exit-point in another country, e.g. to circumvent regional locking
In all but the first case it does not really matter how safe it is. You could just use an unencrypted GRE or IPIP tunnel. In the second case it could be problematic but it probably isn't, the ISP likely is not going to the trouble to look in such tunnels anyway.
So in fact this security is only burdening the router, which has to encrypt and decrypt everything, and it has costs in performance due to the larger headers of encrypted/authenticated tunnels vs the simple ones. With a better router (like RB750Gr3) you won't be troubled by the encryption CPU overhead, but you still have the header overhead.
Of course when you want to use an existing "VPN provider" (in the sense of providing a different exit-point) and it likely does not provide the option of using such simple tunnels. So then you are obliged to jump to the "secure" hoops, even though it is not really needed.