Unbeatable races are races with too much depth or too little such as when there is an odds-on favorite [If I bet on the thing it will loose and if I bet against it, it will win]. Betting in say 50 [name your number] of these races over a year will show a [big?] loss, so 'collectively' they are unbeatable races.

Also, we are all looking for value [or should be] on what we believe can win a race. Often it just isn't there. If our overall win strike rate is 1 in 4, we better make sure our winning prices [averaged out] are better than 3/1 or all our bets are in unbeatable races.

There are plenty of races and prices to choose from.