Wait for Private Servers
Fallout 76 is designed to play with other people so the lack of an offline mode shouldn't come as a surprise.
In response to a question about a potential offline mode, the company's Pete Hines states that "it's a server based game" and that he doesn't see the company "completely re-engineering it to somehow be an offline game that is entirely client based."
This means the closest thing you'll get to an offline mode is playing it on a private server.
In response to a question about private servers, Hines says the company plans to "support private servers, including the ability to use mods on those servers, sometime after launch."
If you think private servers and/or mods are going to be important to your Fallout 76 experience, you might want to hold off on buying the game until 1) we get more information about their release window 2) they're released.
5 Reasons to Pre-Order Call of Duty: Modern Warfare & 3 Reasons To Wait
<8 / 8Wait for Bigger Call of Duty: Modern Warfare DealsIf you want to save money, wait for Call of Duty: Modern...
10 Best Surface Pro Alternatives in 2019
<>8 / 11HP Elite X2$1.00 from HPThe HP Elite X2 is a Surface Pro alternative that packs in full PC...