You're missing the point. These people didn't need a visa, because they were already citizens. It wasn't until much later that it was agreed the Empire was over and Commonwealth citizens would not automatically qualify for British nationality. What the Tories are trying to do is retroactively apply that to the people who spent their working lives contributing to Britain, so that we won't have to repay them with care in their retirement. It's a simple attempt to keep the pension system ticking over for their core voter base.
The killer irony is that to a man Britain's racist filth, who voted Brexit to get back to the glory days of Empire and "kick out the darkies", fail to understand that the Empire is the sole reason said "darkies" came here in the first place.
(NB: "racist filth" and "Brexit voter" is not a reversible equation here. All racists voted to leave the EU; not all people who voted to leave the EU are racist.)