Lisa does explain (perhaps later in the course than where you're at) that B and F are a little tricky as they don't lend themselves to open chords. She also mentions that B and F are very uncommon keys to use for guitar based music, presumably because of this reason - the chords are a bit lacking. She does actually touch upon B7 to use as a substitute for B and 7th chords always sound really nice.

Stick with the flow of the lessons. I know the temptation might be to fill in the gaps yourself but Lisa does a great job of covering all this complication. Barre chords will get covered later. They're not as nice as open chords but given you don't have much choice with B and F they will have to do!