"You can pollinate crops using bees kept in captivity. Many crops are pollinated this way." ... as much as I may appreciate the sentiment, it seems to me that we - the global we - have become adept at finding band-aid solutions (especially when it involves technology) to symptoms but rarely address and attempt to fix the actual causal factors, i.e. the problem. I would hazard to guess this is for primarily two reasons. First and foremost, it requires grass roots and pervasive change - change in values, behaviours, beliefs - and change is often difficult. Second, there appears to exist a pervasive view that sees us humans as outside of nature rather than an integral and dependent part of the whole.
Most crops are not. Many plants rely on specific insects for pollination. And domesticated honey bees can never hope to match the rest of the insect world in numbers.
You wouldn't need domesticated bees to match the rest of the insect world's numbers. You'd just need to enough to pollinate crops. And bees can pollinate many, many different types crops. Also, you can always pollinate by hand if need be, which is how vanilla in Madagascar is pollinated. I'm not saying declining insect numbers are good, I'm just saying worrying about a crop-apocalypse is probably unfounded.
If every foodstuff costing as much per flower as vanilla - a spice usable in famously small quantities - isn't a crop-apocalypse, what is?
Mason bees, for instance, do ~3x the pollination work per-bee, and are relatively easy to accommodate in any garden or yard: