The biggest barrier to Lean UX in any organisation is resourcing: if you're the only UX researcher in the proverbial building, it is impossible to work in a cross-functional team, or indeed to commit to the rapid iterations that the work requires.

Having experienced two corporate lifecycles, in the early stages when there's just one researcher, 100% of that role is putting out fires. If you're embedded too late, at least the first year will be spent doing reverse discovery until you learn the basic information about user needs that you should have had in the first place.

Only then can you work towards the Lean UX model.

While a 1:1 ratio of products/teams to researchers might not be feasible, at least aim for one researcher per product suite. If you have at least one designer per product suite, that's a start, but it's no substitute for having dedicated research support.