I don't think there is a great filter. I think there's an easy solution to the fermi paradox that doesn't require great filters, we're just the first intelligence in this galaxy.

Here's my reasoning: intelligent species that manage to develop space travel probably do tend to expand out into their galaxy. When they achieve this level of technology they can settle most of all of their galaxy in a matter of 10,000 years or so. That time period is very brief on an evolutionary scale. It's estimated that life began on earth 3.7 billion years ago. That means it took about 3.7 billion years for earth to produce intelligent life, and then from that point it would take a mere 10,000 years to reach modern day, and 10,000 more years to settle the whole galaxy. That expansion happens so quickly compared to how long it took the planet to develop intelligent life, that the chance of two civilizations rising at the same time becomes very small.

It all boils down to this: there are no intelligent aliens out there in our galaxy, because we are the first intelligent species in our galaxy. We know we're the first because if we were second, then aliens would already have settled this star system.

Probably there are lots of alien civilizations out there in the universe, but they're in different galaxies.