Marcus' core passion is social justice which he describes as 'ensuring that everyone has access to opportunity, is valued and participates in decisions that affect them'.

A founding partner at SGS, Marcus is formally qualified in commerce and urban planning. He has practised as a consultant for much of his career, though he has also worked as an academic, local government town planner, Ministerial Adviser and senior bureaucrat in State and Commonwealth Government agencies. He is an expert in regional economic development, housing policy, infrastructure funding and metropolitan governance. This includes writing and co-editing two books on urban management.

Marcus is a past National President of the Planning Institute of Australia. He has served on the Commonwealth Government’s National Housing Supply Council and a similar advisory committee set up by the NSW Government. He is a Ministerial appointee to the Housing Supply Expert Panel for South East Queensland and sits on the Ministerial Advisory Committee on planning mechanisms for affordable housing in Victoria. In late 2022, Marcus was appointed to the Interim National Housing Supply and Affordability Council. He is a former Board member at VicUrban (now called Development Victoria).

Marcus has a passion for sharing knowledge and informing robust debate and is an Associate Professor (honorary) at Melbourne University (Architecture, Building and Planning). He also holds Adjunct Professorships at RMIT University and UNSW.

Marcus is a regular speaker and frequent presenter at conferences across Australia and internationally. He is a sought-after commentator on the need for metropolitan reform. In 2018, Marcus co-edited a book titled Australia's Metropolitan Imperative: An Agenda for Governance Reform, which argues that Australia’s largest cities need their own democratically mandated governments.

In 2019, Marcus was awarded Life Fellowship at the Planning Institute of Australia. During the award ceremony, industry peers and colleagues described Marcus as: 'One of the most outstanding thinkers and leaders in urban planning in Australia' and 'Having a profound influence on the Australian urban policy across Australia' and 'A true humanist who always has the best interests of the community at heart'.