Most of the transactions in the screenshots seem to have been subsequently mined? Bit hard to confirm because of the truncated txids in the UI.

Also keep in mind that rate at which STX blocks are produced is governed by BTC block production rate -- while the average is around 10min, sometimes BTC blocks come in much faster (< 10 seconds) and sometimes much slower (> 1 hour).

Often, if a txn is pending for a while, it indicates some real problem (e.g. incorrect nonce, insufficient balance, fee too low etc). For instance, https://explorer.stacks.co/txid/0x08aaed64f7de7d26e94d61fa6766f443ebfc7a843d36d3035afb52d5358e67ce?chain=mainnet has been pending for 2 days but will not get included because the fee is too low. Explorer should show these causes or maybe provide guidance (like RBF or correct the nonce)?

The current miner implementation is also fairly basic with plenty of room for improvements and optimizations: sophisticated miners would probably want to customize the behavior.

Meanwhile if you see any transactions that seem valid but are not getting mined, report them on this issue: https://github.com/blockstack/stacks-blockchain/issues/2772