The phrase "are often too large" is correct and usable in written English.
It can be used when discussing the size of objects, quantities, or concepts that exceed a desirable or manageable limit.
Example: "The portions served at this restaurant are often too large for one person to finish."
Alternatives: "tend to be excessively large" or "frequently exceed the ideal size."
As a result, cooling systems are often too large for most normal driving modes.
They argue that urban schools are often too large to give students the attention they need.
Graph data in modern scientific and engineering applications are often too large to fit in the computer's main memory.
California's institutions are often too large or too small to govern properly.Proper regional government would be better.
But they are often too large to lock in a car, so can be a problem to secure.
Often these objects are often too large, delicate or otherwise inappropriate to be included in their life storybooks.
Yet, the size of most microbial communities resident in natural ecosystems is often too large to be resolvable, the interaction landscape too complex to chart, and the communities too difficult to manipulate.
In many modern applications including web analytics, search and data mining, computational biology, finance, and scientific computing, the data is often too large to reside in a single location, is arriving incrementally over time, is noisy/uncertain, or all of the above.
Although combinatorial chemistry methods can be used to augment existing compound libraries with novel drug-like compounds, the broad chemical space is often too large to be explored.
In case A, especially in the beginning, the content of a task was often too large but was improved during the pilot project.
To cater different network models and design goals, the value for k is often too large to achieve several conflicting design goals, simultaneously.
