When taking a gateway to the outer end islands, it is possible, although rare, for the player to end up in such an isolated location that they cannot reasonably escape if they do not have ender pearls, blocks and/or an elytra and firework rockets on them, even if they do have a pickaxe. I'm unsure whether Mojang would be interested in fixing this. This has been an issue with the obsidian platform for a long time, and no experienced MInecrafter goes into the dragon fight without bringing some blocks or a pearl with them. But since gateways tend to be more generous - at worst, leaving the player with enough blocks that they can build a short bridge, get an enderman to spawn, kill them, and then pearl to the mainland - players may not be prepared for a truly terrible spawn where they have only 10 blocks to work with.

To reproduce

1. Create a creative world with seed 5917284831799768604

2. /execute in minecraft:the_end run teleport @s 0 60 70

3. /kill @n[type=ender_dragon]

4. Throw an ender pearl through the gateway that has spawned in front of you
5. Ponder the unfortunate situation you would be in if this happened in survival

For comparison, repeat the steps above with seed 193221013593822 instead. Doing so results in what I would call a "very bad" spawn, an annoyance which can be overcome with sufficient patience and ingenuity. With the original seed, the player might theoretically be able to escape through insanely lucky block drop velocity and a healthy pickaxe, but for practical purposes it's just not possible.

Thoughts on a fix

If this is a valid bug, then it's unclear what the best fix might be. It may be necessary to redesign end gateways so the player can reliably get back to the main island, similar to how nether portals can be used without issue in skyblock worlds. Making gateways an end highlands-only structure would fix the particular instance I found but would come with its own challenges.

Related issues

MC-141823 is only somewhat related, but it may be useful to review it when deciding how to resolve this.