Buy or build and what is AI Middleware

The technology in the field of AI is developing on a weekly basis. It is no longer about the large models of hyperscalers, but rather about which models are suitable for which processes. speeds, accuracies, context uncertainties and costs are just some of the parameters. Then there is the issue of data with high-performance RAGs that can process multimodal data. Individual processes will become sequential process steps and then autonomous processes, i.e. agents within the company. How is it possible to manage all of these topics, constantly develop them further and always rely on the right technologies? What do I do myself, what do I buy in is one of the most important questions and what is middleware anyway?