Ray of frost does a number on these guys. I ran the Lost Mines of Phandelver for some buddies a while ago, where one of these shows up in the final dungeon.

The wizard simply kept ray of frosting it, reducing its speed to 0, allowing the party to pick it off easily.

For those of you clearly afraid of this thing or worried that it is somehow overtuned, please take a nice long look at its movement. Depending on the setting of the fight the PCs can just outrun this thing easily and whittle it with basic cantrips worst case scenario. It's literally blind beyond 60 feet.

so cute!!!! slay queen!

Once you realize move speed is only 10 its really easy to just stay far enough away and keep doing ranged attacks on them, easy enough 

Don’t know if you’ll see this but

I was just  working on the Ochre Jelly encounter in Lost Mine of Ph. And was having the same thoughts you presented in your post (if the player is engulfed or grappled when covered by the jelly) One other thing I was concerned about was if the character who was covered by the ooze would take damage from the attacks his fellow players inflict on the O Jelly especially if they weren’t careful or weren’t able to avoid hitting the area where the player was in the jelly. 
That would be pretty bad for that player but it seems that is what would happen. 
What do think? 

am i able to eat this

They're inedibly sour, without alchemical processing to make them more palatable.

Butter Gummies

I just made a small one stick to one of my players rapiers when they hit it. It was hilarious because the dwarf player did not care at all, and just hit the other one. The dwarf hates humans. The one with the yellow blob on their rapier is a human. GMing Icespire Peak.

I also made one of these drive a carriage as a form of taxi in a different campaign. The players are super suspicious of it. It has no malicious intent.

Quote from BlueJayBuh >>

Dragon of Icespire Peak has two of these up against 3 level 1 players - I feel like my players are going to get destroyed? Do you think I should only give them one?

 WAY LATE, but I just nerfed them. A lot.

Quote from SeanBrian >>

Once you realize move speed is only 10 its really easy to just stay far enough away and keep doing ranged attacks on them, easy enough 

 Tell that to my party of two close range fighters and a wizard who barely uses anything but burning hands.