Modern applications are generally distributed in nature, e.g. in last 4-5 years, all the solutions that I architected were Microservices based. Distributed applications have a different philosophy, many architecture characteristics or concerns that were afterthoughts in traditional applications, are now mainstream. Infrastructure is one such concern that should concern an architect, a developer or product owner at a very initial phase. Infrastructure is actually a First Class Citizen.
Infrastructure needs in a traditional software systems are usually static in nature. I seldom saw anyone paying too much attention to it and it is mostly left to IT engineers. Architects and developers are only concern to define infrastructure specifications e.g. RAM or CPU and that too at a later stage. These infrastructure requirements has almost no effect on how application is crafted or developed. The most obvious consideration during development is limited to when system is stateful and behind a load balancer or it needs to keep a flag (e.g. in case of scheduler).
Things changes dramatically in distributed application, especially in microservices. These systems are dynamic, e.g. one of the basic ingredient of microservices is elasticity which means network addresses of resources will change frequently. Traditional methods of defining a static list of IPs will not work anymore and some new patterns are needed (Service Discovery). Similarly, observability is another concern that is not so obvious in these systems. There is no single log file, rather sophisticated infrastructure needed for logs aggregation, or tracing is not straight forward but distributed in nature and require another framework.
All of these concerns needs to weaved in the application development itself and in fact needs attention at solution phase. Infrastructure platforms, tools and framework influence development greatly. Clearly, Infrastructure is a primary factor of architecture and development.