Right’o.
The 1000ft view.
First, the most obvious limiter is your winter volume. That’s definitely going to be your easiest gain. A very easy fix. Just do everything possible to inch up your winter training volume.
Maybe try a very simple approach of just beating your own winter volume from last year. I use monthly hours on Strava and a superb plug-in for Chrome called Elevate. It has a simple graph comparing yourself, to yourself.
If you want to be better than last year, you have to train harder, longer or smarter. Any combination works. It just has to be better than what you’ve previously done. You are competing with last years version of yourself, smash that fool. 
I’m certain that if you continue to train in the manner you’ve currently been training, but keep your winter hours higher, you’ll see improvement. If you make further improvements, for example, better distribution of training and better nutrition, you’ll improve further.
You’ll also be benefitting from already having the adaptions from your previous years of training. It’s basically a case of the rich getting richer.
The easiest option is literally what TrainerRoad often recommend. Just add more Z2 to your existing training. It could be as simple as adding just 15mins onto 4 workouts a week. There’s 1hr more aerobic training a week. Per year is the interesting bit, it’s 52hrs more. That’s substantial.
It’s my experience that many, if not virtually all amateur cyclists are lacking in base aerobic fitness. It can almost never be deep enough. It’s surprisingly more important in cyclocross than I previously understood. Having a well developed base aerobic system greatly effects the speed of your recovery between efforts.
This is almost the entire game in cyclocross. Punch, recovery, punch, sustain…repeat.
NEVER give up your group ride. This is supposed to be fun.
Hypothetically something like this for ‘general’ structure.
Monday - Rest
Tuesday - Z2 Longer workout, tempo intervals if feeling strong
Wednesday - Z2 Endurance
Thursday - Hard day, intervals, hard ride outside, whatever is relevant
Friday - Z2 Endurance or recovery day
Saturday - Z2 Endurance or recovery day
Sunday - Group ride, pick segments, race, sprint, attack, have fun, go nuts
You be the judge on what day you choose for recovery day, Friday or Saturday. Base it on weather, fatigue, goals, life stuff, everything. You should be well rested for your group ride. It’s one of only two key hard days per week. Your other hard day is either Tuesday or Thursday. You’ll be well rested on Monday after a day off. However, it is not far removed from Sunday’s group ride. You need to experiment with either day. Also, when you are feeling strong and well recovered, you could add an additional hard day occasionally. Be careful with this though.
Remember, only you truly know your own body. The more aware you are of your own fatigue levels and general well being, the better you’ll be able to adjust your own training prescription. This is vital, as no pre prescribed training plan can possibly factor in your unique life situations etc.
Good luck. I hope you crush your 2020 self 