There is always a risk when people are specialists in a particular discipline that the solution to any presenting problem is whatever they are expert in. So, for example, L&D people might always think that the answer is some sort of learning intervention (or worse still, always think that it is a training course). This is like the tradesman coming to fix a problem in our house and only bringing a hammer with him. External consultants with their proprietary solutions and specialisms can be a bit like this, but so can internal specialists.
The reality meanwhile is that any business situation is a complex interplay of people, their capabilities, structures, processes (and systems) and organisational culture all set within a context of the business strategy and external environment. The most important part of improving performance is understanding the problem and what changes, interventions, approaches etc. will lead to an effective solution. The focus needs to be on what any intervention achieves rather than the activity itself
For example, I have been working in partnership with four client organisations of various sizes and sectors to help them move through a period of challenging change. If this was described in traditional HR discipline terms, we could say that it includes workforce planning, structure and job design, job evaluation and pay design, coaching, new models of service delivery etc. etc. But actually, all the work with these clients is much more integrated than that. It is about working with them so that they can respond to the changing external environment (increasing customer demands, reduced funding and so on) in a way which allows them to survive and thrive.
I have helped these clients make decisions about what are the right solutions for their situation and then worked with them to identify the best route to implementation and how to manage the change. Often, this is the client doing things for themselves with my support and challenge. Sometimes, I will carry out specific tasks in the programme (such as designing jobs or run a coaching programme) or it may be about finding a third party who can deliver a specific solution (such as an assessment centre). But whatever the specific interventions, these clients value someone working alongside them so that the solutions remain integrated and focused on improving Organisational Effectiveness.