It all comes down how you define Far Right and Fascist.
Actual Fascists from 30s/40s were anti democracy, anti minority, anti--women and pro aggressive militarism/imperialism.
Farage is not anti democracy, he is fine with women leaders, educated women or in business. He has a party with prominent Muslim members he is anti mass immigration sure, but he believes in limited migration. He has consistently thrown out people inside parties he has run for racism. On the military his beliefs are fairly standard. You can argue he is weak on Russia, but so are many Euro leftists. He isn't planning to invade anywhere. Now he is filling the party with some Tories hardly the act of a radical.
So you end up with a right wing populist party, not a Fascist one, yet compared to the ones in Europe it is hardly that radical.
The tendency to exaggerate is a key problem in todays politics. One tactic which fails again and again is painting people thinking of voting reform as evil extremists. Left has talked about Farage being Hitler like for decades, it doesn't make any sense and makes them look like they want to duck conversations. You can't shame voters into backing you. The right do it all the time Starmer is a communist. That sounds so dumb.
The wider issue with Farage is the charge of incompetence, and dislike of having anyone challenge his authority. His record in party management is shambolic. He thought both Boris and Truss might be worth backing. A Reform government might be a total train wreck.
Farage is not unbeatable. It would require the left/centre to focus round one party in 2028/9 though. This is the awkward fact. Again this undermines the rhetoric Labour/Lib Dems/Greens plus the Tories all kind of hate each other enough, that in practice they and voters in general are likely to let Reform win by default. If Farage is really the ultimate evil then surely people would be ready to help Ed Davey win for example. Only in practise few think like that. All the parties look kind of useless right now. That ultimately is on them.
We are probably going to find out what a Reform government is like. If it truly messes up then it will be out in 5 years.