Few ufologists understand anything about the level of technology that the advanced races visiting Earth have, but it is true that it would take much more, even for them, to be buzzing all over the Universe.
These are a few facts that I know from the alien races themselves that may help things to be better understood.
Basically, the advanced races throughout the Universe[s] each cover their own comfortable area of travel, but all network between each other, overlapping area to share information across space.
Of course some of the races are much further evolved and advanced and can cover more area, and have greater histories of areas.
Some races are more remote and isolated and some areas are more densely populated.
There is a system of order governed by the most advanced and capable races, and supported by all advanced life in space.
That does not mean there are no conflicts - it just means that all agree to solve conflicts by certain criteria, sometimes taking a long time, and often not getting exactly what each wants, but all getting what everybody wants the most, which is peace.
Without peace maintained in first place despite conflicts, a race does not progress very well, or even at all, not with others, and not even with itself.
The advanced intelligent life in our galaxy is part of a union of five galaxies.
There are over 5200 advanced races of life in this union.
There are a relative few primitive races in the area who are not participating in the union yet, like us.
There are 103 other races in our galaxy who are about as primitive as we are, having their visiting life organized together to begin working openly with the newer race.
All advanced races visit their neighboring worlds of life.
All the races that visit Earth are much further advanced than we are - hundreds of thousands to millions to billions of years - and all come from around us, close by in our galaxy.
Almost all are from our own arm Orion, and just a few from the neighboring two arms.
There are 218 races visiting Earth, and they all know each other and work together here now.
The advanced races can travel as we normally do, only they can move at up to near light speed comfortably, to cross shorter distances in normal time, but they use dimensional technologies to travel vast distances between worlds.
Other dimensions have different values of time, and the result is similar to tossing a ball in a speeding car or running up an escalator.
Even with the use of dimensional technologies, it still takes a long time to travel between worlds, so the visiting races set up here to stay while they work.
The average time it takes the visiting races to get to Earth is two weeks.
They travel here in their own crews, in large crafts for each race, which are parked outside of our atmosphere to live in for their stay.
The smaller crafts we often see approaching the surface of our planet are shuttles from the larger crafts.
The individuals working here take turns to go home to visit their families once or twice each year.
Open vs Sneak
At virtually all other worlds, the visiting life come and go openly.
At Earth, our visiting races have to sneak in and out very carefully while trying to educate the bravest select, but barely capable, barely willing individual humans.
These humans, when discovered by Earth powers, are so then named as targets for threat, seduction, bribe or worse - tools for control of the alien races, and information about the alien races.
This amounts to blackmail by hostage.
Carefully staged, blatant shows of alien presence are to insist their reality to all on Earth, but due to general human ignorance, still today this creates more confusion to be diabolically used by Earth powers against the reputations of the alien races.
And in the publics' mind, the confusion still lends credibility to the propaganda being generated about the alien races by Earth powers.