Normally I like to see a 2" for the washer drain.
Your's looks to be 1.5"
A simple fix would be to cut in a santee, add a short piece of pipe with a p-trap, and run a standpipe for it.
Where the washer goes in now, you can either continue that as a vent through the roof, or worst case, AAV it.
A nice upgrade would be to cut in a 3x2 wye and run the washer drain in 2"
That would be the code way to do it. That and extending the vent up and out.