r/gamedev zeroed in on PC Gamer's March 18, 2026 report about why Cities: Skylines 2 struggled so badly in development and after launch. According to the report, Colossal Order CEO Mariina Hallikainen said the studio "completely overestimated" what Unity would be able to deliver at the start of the project, a candid admission that gives the sequel's long-running technical problems much clearer context.

What Hallikainen said

Hallikainen said the team planned major parts of the sequel around Unity features that were not yet finalized.
The goal was to future-proof Cities: Skylines 2 for a very long post-launch life, but some of the technology the studio depended on did not fulfill its promise.
That forced the team to spend significant time replacing missing functionality or compensating for systems that were not working correctly.

Where the engine fell short

PC Gamer says Hallikainen later clarified the issues in an email, pointing to general engine instability, missing core features in the HDRP shader pipeline such as interpolators, and the lack of long running job support in ECS. That is a more serious problem than a normal round of late optimization. It suggests the project was built on technical assumptions that stayed unstable for too long.

The explanation matters because Cities: Skylines 2's problems were never limited to one headline issue. Players dealt with weak performance, frustration over missing or thin-feeling features, slow progress on modding support, and long delays surrounding post-launch content. Hallikainen's comments frame those outcomes as the downstream effect of a foundation that did not mature on the schedule the studio expected.

Why it matters now

This is an important story because it speaks to a broader production risk across the industry. Studios often build long-range plans around engine roadmaps, middleware promises, and future tooling, especially when they expect a game to run for years after release. If those assumptions prove too optimistic, the damage does not stay inside engineering. It reaches feature scope, polish, scheduling, and community trust.

At the same time, Hallikainen did not present this as a breakup with Unity. PC Gamer reports that Colossal Order still has a good relationship with the engine maker, and that its next PC simulation game is also being built in Unity. The real takeaway is narrower and more useful: the studio now sees its core mistake as betting a flagship sequel on technology that was not yet proven in production. That makes this less of a blame story and more of a practical postmortem on engine risk.

Source: PC Gamer · Reddit discussion

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r/gamedev: Cities: Skylines 2 Boss Says the Studio Overestimated Unity's Capabilities