As the community grows, please don't go making tag synonyms or burning tags without consenting meta unless it's really obvious, but even then it's not a bad decision to ask meta. A lot of the time others can provide good thought and argument that you haven't thought of. Even if they can't provide more argument and agree with you, that's really good indication that it's the correct move in which case you can do it then :)
Now to your question.
Tag synonyms and burnination almost always have to be handled on a tag by tag basis. Lumping together a lot of them to be handled at once is rare and should not generally be done, even in a list format in a meta question. With that being said I'll give my opinion on each set of tags you listed with the logic behind it so that we can apply the same logic to other tags in general. By doing so, it's more so support for my argument than anything else.
For every tag that we have, it should be possible to create valid questions using only that tag. If it doesn't make sense or add value to only have that tag, the tag shouldn't be around in the first place.
Also, each tag should be able to be applied to lifehacks as we have them defined in our scope. This means the tag should directly describe why the lifehack itself is needed and what the lifehack relates to.
Now, let's look at the cases you brought up :
Individual holiday tags should remain - I can see these being useful, particularly when it deals with creating things that deal with particular holidays like this question (which also has other good tags, but it proves the point that a holiday specific tag may be useful).
Pets are not the same thing as animals - For example dealing with raccoon or other critters would not fall under the scope of pets. As such, both should remain, but we should make sure that they are used appropriately - pets for pet questions and animals for more non-pet questions.
General device type tags should remain - Dealing with phone problems is completely different than dealing with internet or a laptop. All of these fit under technology, but in that case technology helps as a general descriptor of the question and can be used to filter for more tech savvy lifehackers. Also, things sometimes exist that fit under the scope of technology that don't fit any of our more specific tags which is okay, it just proves that the tag is necessary.
Burn insects - I see no reason to keep it around as pest-control handles all insect related activity that I can think of and there can't exactly be a lifehack dealing with only insects (if someone has a good example showing the need for insects, please comment). The question that uses it now has much more to do with treating a medical effect than it does with an insect.
This same general logic can and should be applied to other sets of tags that we have now as well as in the future.