The software was "reproducible" in that the same starting conditions produced the same output, but that didn't mean the _science_ was reproducible, as every study used the same software.
I repeatedly brought it up, but I wasn't advanced enough in my studies to be able to do anything about it. By the time I felt comfortable with that, I was on my way out of the field and into an non-academic career.
I have kept up with the field to a certain extent, and there is now a project in progress to create a fully independent replacement for that original code that should help shed some light (in progress for a few years now, and still going strong).
This is the difference between reproducibility and replicability [1]. Reproducibility is the ability to run the same software on the same input data to get the same output; replication would be analyzing the same input data (or new, replicated data following the original collection protocol) with new software and getting the same result.
I've experienced the same lack of interest with established researchers in my field, but I can at least ensure that all my studies are both reproducible and replicable by sharing my code and data.
[1] Plesser HE. Reproducibility vs. Replicability: A Brief History of a Confused Terminology. Front Neuroinform. 2018;11:76.
Something like this is the norm in some more mathematical fields, where only the polished final version is published, as if done by pure thought. To build that, first you have to reproduce it, invariably by building your own code -- perhaps equally awful, but independent.
The fact that we can have that option is an amazing opportunity that a confluence of attributes of software (specificity, replayability, easy of copying) afford us. Where we are not exploiting this like we could be, it is a failure of our institutions! But it is different-in-kind from traditional reproducibility.
More concretely, it is 100% fair (and I might argue necessary) to demand more of our institutions and work to improve their failures. I'm sure many researchers have encountered publications of the form "we applied <proprietary model (TM)> (not explained) to <proprietary data> (partially explained) after <two sentence description of preprocessing> and obtained SOTA results!" in a reputable venue. Sure, this might be even less reproducible 200 years ago than now, but the authors would also be less likely to be competing with you for limited funding! Debating about the traditional definition of reproducibility has its place, but we should also be doing as much as possible to give reviewers and replicators a leg up. This is often flies in the face of many incentives the research community faces, but shifting blame to institutions by default (not saying you're doing this, but I've seen many who do) is taking the easy road out and does little to help the imbalanced ratio of discussion:progress.
But repeating the simulation a large number of times, with different random seeds, should produce statistically similar output if the code is rigorous. So even if each simulation is not reproducible, as long as the statistical distribution of outputs is reproducible, that should be sufficient.
There are some kinds of code (a script that controls a sensor or an actuator) where I think that doesn't match up well at all. There are plenty of kinds of code where they are, in fact, simply crunching numbers produced earlier. For the latter, I'm honestly not sure the best way to treat it, except to say that we should be sure that enough information is included in some form that replication should be possible, and that we keep in mind the idea that replication should involve human interaction.
Edit: more careful phrasing.
On the contrary; in that case there are four possibilities:
a: your algorithm doesn't work at all, and your observations are a artifact of convenient inputs or inept measurements.
b: your algorithm works, but the description in the paper is wrong or incomplete
c: your algorithm works as described, but the replicater implemented it incorrectly
d: other
Having the original implementation code is necessary to distinguish between cases a and b versus case c, and if the former, the code for the test harness is likely to help distinguish a versus b. (Case d is of course still a problem, but that doesn't mean it's reasonable to just give up.)
I'm all for more transparency, and this includes making codes and data public as much as is reasonable. But the real test is if someone can independently replicate the result, and how to incentivize replication studies (in both computational and experimental science) is also important, and in my view should not be divorced from discussions of reproducibility.
Edit: rewrote to clarify my position.
I agree that this is a good property for scientific code to have, but I think we need to be careful not to treat re-running of existing code the same way we treat genuinely independent replication.
Traditionally, people freshly constructed any necessary apparatus, and people walked through the steps of the procedures. This is an interaction between experiment and human brain meats that's missing when code is simply reused (whether we consider it apparatus or procedure).
Once we have multiple implementations, if there is a meaningful difference between them, at that point replayability is of tremendous value in identifying why they differ.
But it is not reproducibility, as we want that term to be used in science.