Stuck at a running plateau: How do you guys break through it?

Hey everyone, I've been running consistently for about two years now, mostly 10k distances, and I feel like I've hit a wall. My times just aren't improving anymore, no matter how much I push myself on my regular routes. I'm doing about 4 runs a week, a mix of steady state and one longer run.

I've tried adding a bit more mileage here and there, but it mostly just makes me feel more tired without any real speed gains. I'm wondering if it's a training intensity issue or if I need to incorporate something totally different. My easy runs feel easy, but my 'hard' runs don't seem to yield results.

What strategies have worked for you when you've felt stuck? Are we talking more tempo runs, interval training, or should I be looking at hill repeats? Any specific workouts or changes in routine that really made a difference for your speed and endurance? Really keen to hear what's worked for others.