Wrong, modern ventilation systems recover up to 90% of the heat.
This works at -10 degrees outside and 21 inside.
But it also works just as well at 30 degrees outside and 21 inside.
It is even noticeable that the delta T in summer is much smaller.
I have already calculated several times here in the forum how little heat gain there is through running ventilation in summer.
So keep the ventilation running both in summer and winter to maintain a pleasant indoor climate.
A control depending on humidity and CO2 can make sense.
Temperature should not influence it due to heat recovery.
I can confirm that, the house is always pleasantly tempered despite continuously running controlled residential ventilation. Unfortunately, I don’t have an enthalpy exchanger, so currently about 70% on the hygrometer. But it is not unpleasant and as far as I understand, not problematic either.
Besides, (of course?) when I am at home I often keep the terrace door open wide and for a long time, at least when the temperatures allow it.
Most central controlled residential ventilation systems have a user interface (web, app) through which end users can make adjustments. I have adapted the ventilation to my personal needs (when and how much to ventilate, dehumidification, reduced, nominal and intensive ventilation). Besides the scheduled operation, sensor-controlled operation would also be possible, but I only have one humidity sensor installed, so it works better for me on a schedule.
Regarding energy savings: for that reason, such a system is never worthwhile. Mine has recovered about 160 kWh in around 2 years (according to the system).
Since this is thermal energy, I estimate a COP of 4 = 40 kWh electrical energy times 40 cents ;-). With system costs of over 10K and annual filter costs of about €100, anyone can calculate that it is not worthwhile for this reason.