Why do we need to get Back to the Gospel?

In the US the common consensus among many biblical Christian leaders is that 90% of the visible Church is void of the gospel, unsaved, and of the world. The vast majority of those claiming to be Christian are not saved because they are in false teachings, follow a Jesus that never existed, and believe a false gospel that contradicts the gospel of salvation by grace alone, through faith alone, in Christ alone.
Satan is leading multitudes astray by subtle, incremental lies. Lies that are mixed in with just enough truth to appear real to those without the discernment to spot a counterfeit.

"And then many will fall away and betray one another and hate one another. 11 And many false prophets will arise and lead many astray. 12 And because lawlessness will be increased, the love of many will grow cold. 13 But the one who endures to the end will be saved. 14 And this gospel of the kingdom will be proclaimed throughout the whole world as a testimony to all nations, and then the end will come." - Matthew 24:10-14