I grew up in England, but didn't wear shoes indoors because of my parents culture. My husband's mother wore shoes indoors (and had a dirty flat) but my husband chose not to in his bachelor pad when I met him and it was rather clean.
When my husband and I bought a home together, our baby was always all over the floors, crawling, playing - and I was glad we didn't wear shoes in our home. I can also curl up on the sofa or go up and down the carpeted stairs without worrying about trailing mud. I've visited other homes in Surrey and a lot of people don't wear shoes indoors.
Most people wash their feet every day and wear clean socks every day - which is cleaner than shoes. If you have a foot infection/smelly feet, you should go to the doctor and get that sorted. People who clutch their pearls at taking their shoes off and label shoes-off homes as 'common' must have minions laying a red carpet out for them wherever they walk, so their very uncommon shoes must never have remnants of dog shit, people's spit, rotting food, bird shit and general rubbish on them.
How uncomfortable is it really, to only wear your socks in someone's home. These same people are perfectly comfortable with bringing dirt into other people's homes! Get some decent socks and get over yourself.
I have had elderly guests before - I've not said anything to them and they've kept shoes on, but they didn't move around much and I can understand it's hard for them to get shoes on and off, so I didn't mind.
If you aren't elderly and your biggest worry is that you will get out of breath taking your fucking shoes off - as a previous person mentioned - then you have a big problem.