I would disagree with this. In general, the algorithms are well known and only need to be implemented once. Doing problem modeling to solve real problems is where the action is for optimization.
> the algorithms are well known and only need to be implemented once
To an extent. The basic algorithms are well known (simplex, interior point), but there is a lot of scope for improvements - this is why the big commercial solvers can be orders of magnitude faster than the best open source ones. Still, even if the algorithms are not well-known, they do only need to be implemented once.
For integer programming, though, there can definitely be value in problem-specific heuristics for branch selection and rounding.