I think the way you thank someone should be proportionate to what you are thanking them for and how much effort they have gone to for you.
When I was a child we were expected to write thank you letters for Christmas and birthday presents. A birthday card with a £10 note in it merited a handwritten thank you in the post.
Now texting is a thing, it's totally fine to just send a quick message to thank someone for sending you a birthday present or some flowers. And similarly, if someone has had you to stay or round for dinner, you should pre-emptively thank them by bringing flowers or wine or similar, but then afterwards a text is fine.
When it's your wedding, yes, you will have spent a certain amount per head to feed and entertain your guests, but they have probably also spent a lot of money travelling to get there, often staying overnight, and usually giving a relatively expensive present or sum of money as a gift. They'll have given up at least a whole day and evening to attend, if they've travelled a certain distance it'll be a whole weekend, and if it's a destination wedding they'll have had to use up annual leave allowance as well.
I am not at all anti wedding, I generally enjoy attending them and am happy to make an effort to celebrate with friends when they get married. But sometimes, wow, it costs a lot of money and effort to attend. And it cost many of our guests a lot of money and effort to attend our wedding too, and a lot of them were very generous in terms of gifts as well.
Someone who has given you a handmade wedding cake as a present has not just spent money on ingredients (assuming the financial cost of making the cake is part of the gift).
They'll have spent hours planning it, calculating quantities for the number of guests you have, working out the timings of everything to make sure they don't fuck it up, making sure it's not undercooked, not overcooked, not flat, hasn't risen too much, and that it looks how you wanted it to. They're under a huge amount of pressure to turn up at your wedding with a cake that looks and tastes the way you want it to, and if it doesn't, they can't just apologise and give you a refund the way a commercial cake maker could, they'll have to live with knowing that they fucked up your wedding cake. If they are a professional cake maker then they will be doing something for you for free, or at cost, that they would charge someone else a small fortune for, and that anyone else would charge you a small fortune for. If they're not a professional cake maker then the whole experience may well have been very stressful for them, and will probably have taken many more hours of their time than they were anticipating.
If you can't be arsed to at least write them a nice thank you card and stick it in the post, that's pretty poor really.