Connecting the wire to the connector really isn't the issue, it's what the connector goes to. If the connection is carrying significant amps, it doesn't take much resistance in the connection to make a lot of heat - enough to melt solder and burn the insulation off the wire. I've gone through this twice recently, once with a coffee maker where the heat came from a bad wire nut and the other with a spa heater where the stud and nut corroded.
Of course crimp connections can be bad too - not adequately crimped, or using plated steel connectors. For these, a hit of solder might save the day.