Trenches alone ofc are helpless but they does have also bunkers, tonnels, drones, video cameras, also a lot of civilian stuff is used.... even cheap quadrocopters from aliexpress... doctored or no.
Russia and Belarus does have damn a lot of anti tank and anti infantry mines...
Plus ofc mines and obstacles might just slow down offense , however IF minefields are protected with survillance and when you reach these, they are using howitzers, MRLS etc to shell units.
Also sattelites, they does have some network and....informants....Informants are big problem and they obiviously are promised to get good positions when russia will win and also are paid immediately ....
Minefield alone while is nightmare, is lesser problem than protected minefield. This means that when you reach minefield, they are starting to shell ....