Only unspendable if it costs more to spend then its value in sats. For a layer 1 miner with enough hash (or mining pool), there is no encumbrance as they can include their own transactions.

For the typical user on layer 1 however, I recommend keeping UTXOs above thresholds where the percent lost to transaction fees is uncomfortable. For example, if fees equate to 50,000 sats for a transaction, then this would be a hefty 5% for a 1,000,000 sat UTXO, and a massive 50% for a 100,000 sat UTXO. So DCA, but don't DCA tiny bits to a lot of small UTXOs. Perform appropriate consolidation when fee pressure is lower.

For related reasons, coins in other layers have additional encumbrance. For example, value locked in lightning channels may be effectively dust on your side if the amount is less then it would cost for a main chain transaction. Blockstream Liquid LSATS are pegged 1:1, but any sidechain, altchain etc away needs to take into account the transactional cost to transfer back mainchain if the need arises.

Where feasible, one could consider use of offchain bearer instruments (e.g., opendime, satscard) as a means of exchange without onchain fees. For example, an opendime loaded with 1 million sats could be exchanged for a good or service valued at 650,000 sats, and the receiver could provide change in the form of a lightning payment.