The phrase "are generally very complex" is correct and usable in written English.
It can be used when describing something that is typically intricate or complicated in nature.
Example: "The theories of quantum physics are generally very complex, making them difficult for the average person to understand."
Alternatives: "are typically quite intricate" or "tend to be quite complicated."
Today, users are facing a huge diversity of communication networks and protocols that are generally very complex and heterogeneous.
They are generally very complex and frequently difficult to predict due to the complicated fabricating process and its parameters.
The mill-duct systems for a lignite fuelled boiler are generally very complex and as such, are not yet fully understood.
At the other extreme, the district coincides with the local partnership agreement, despite the fact that the operational solutions adopted for recognising and making operative the network are generally very complex and time-consuming.
One of the major challenges in analyzing a metagenome lies in the reality that metagenomic data are generally very complex in terms of their composition, often consisting of sequence fragments from numerous genomes possibly from different kingdoms (McHardy and Rigoutsos, 2007).
The environmental fate of nanomaterials is generally very complex, but this complexity cannot be sufficiently investigated with the currently available standard tests.
The interaction between the homogeneous reactions in the bulk of fluid and heterogeneous reactions occurring on some catalytic surfaces is generally very complex, involving the production and consumption of reactant species at different rates both within the fluid and on the catalytic surfaces.
Existing visualization software is generally very complex, requiring a high degree of familiarity to obtain the best results, or else it is too simplistic to provide users with the level of customizability needed to get the most out of the atomic coordinates.
"People are generally very excited about it".
The courses are generally very good".
Humans are generally very risk-averse.
