Tanking in The Elder Scrolls Online can be done with any Race. It’s not 100% important to select a perfect race when playing as a Tank.
Tank Race can be chosen based on aesthetics if that is the sort of thing you are interested in, otherwise you would pick a Tank Race that fits in with your Tank experience level and provide you with the most useful Tank related benefits.
Tanking won’t become impossible if you don’t select a Race that is aimed towards Tanking, thing could however be slightly easier if you had chosen a more Tank focused Race, especially at low level and low CP.
In most cases you should choose a Race that improves your sustain as the wide majority of Tanks suffer with sustain related issues, but if that is not the case you should consider the look of your character, whether you plan to play more than one role and if you want to optimise for entering endgame content.