When a software project failed, is it right to consider your architecture failed?

software project failed for many reasons. it is rare to have the solution architecture part of them. but, if the architecture is complex, not readable, and uses technologies team does not know, then that will play a factor. 

Not necessarily, there can be various reasons for a project failure, one of them may be architecture. If it is not easy to add new features, the code is not re-usable, performance too bad and there is no way to improve,  then you can call the architecture is bad.. 

A software project can fail for multiple reasons and architecture is only one of them.  Every architect validates the solution provided against the functional and non functional required before proceeding with technical design and development.  the architecture is gain validated during the integration and performance testing. So the chances of architecture failure is minimized before it reaches the customer.