How simple your tank is entirely depends on what you want to keep in it. I started out simple but ended up where I am now. Once you start keeping different things that need different but non conflicting requirements your system becomes more complex because it has to.
I built this last week
and am adding more stuff to it right now. It's running this with a few more additions to come.
It's still all simple to me because I wired, plumbed, sized, added the control systems and turned it all up myself.
I just used the devil chemical Chemiclean to kill the cyano that built up in the 240 while the filtration was offline and I built the new sump.
What should drive the people in this hobby but doesn't seem to anymore is the desire to keep a certain type of sea creature. That allows you to become an expert on a particular set of requirements for a system and do well in a short period of time.
People now want to buy a tank and put a complex mix of animals in it. To be successful you need a lot of knowledge and thing to support a tank like this. The odds are small IMHO opinion your will be successful on your first or even second try. The animals are somewhat unforgiving of mistakes or poor choices and die on you. This has always been true.
People seem to think bringing home a fish or coral from the sea is like getting a parakeet. You set something up and it just works.
Doing this is more like tending a good garden. It takes time, patience, knowledge and understanding what you are trying to grow.