Personally if i see a PR that I don’t want to see it merged then I would try to shoot it down immediately. So, you can consider those that remain have at least passed the first casual/visual review and have a good chance to be merged or have merits for further discussion even if they don’t make it at the end. However, until one of the core team member (which effectively only left with me and Eugene active lately) has the free time to actually review and/or try the code, they will remain stuck there for a while. I don’t know about others but my excuse is having to take turn to take care of my autistic daughter who just gone through multi-stage eye surgeries, so when I still choose to spend some of my remaining free time for Urho then I actually do it for my own pleasure and not for pressure, tending to pick those that I have interest and are easier for me.
You are also right to point out that the rate of merging slows down after Lasse stepped down from lead role. None of us have the same level of insight of the engine to review and merge the PR as efficient as him even when we have all the time it needs. This is the consequence of losing someone that important to the project. But rest assured all the core team members have a license to kill or merge a PR on their own. Personally I would rather be on the slow side to ensure those newly merged code has the same standard as the rest.
If you still have faith to the project then don’t let this, hopefully, temporary situation to stop you. And if you have more things to contribute, send them in as PR. We need to replenish our ranks and we use those PRs to identify the new candidate.