I actually feel really frustrated about how languages are taught and presented in the UK. (I'm not blaming teachers for a second!) There are a number of (mostly structural) problems including (in no particular order):
We start way too late.
We do way too little.
There is no incentive to learn just one language (like English in many other countries) so a whole smorgasbord is offered, which is not actually that helpful - many children end up doing a bit of everything and make no real progress with any one language. (I don't know what the solution is to this!)
Due to the above (no incentive to learn a particular one), languages are not taken seriously.
Because we leave it so late, there's a mountain to climb when it comes to GCSE, which means the level is way harder than many children can be expected to achieve in the time allocated and there's way too much content, which puts huge numbers of children off. (And the most recent changes to the GCSEs have yet again failed to really fundamentally address this.)
A lot of language-teaching practice that seems to have been passed down for many years now is based on the flawed notion that learning a second language is just like learning your first, so methods are often based on attempting to replicate that, e.g. using pictures instead of translation equivalent words to convey meaning, or exclusively/mainly using the target language in the classroom. This leads to so much frustration for children. (I don't actually know if teachers are still taught to do these things but I know my tutees still encounter them.) Learning a first language is the process of mapping language onto the properties of the real world (or humans' construals of these); learning a second language is a different process.
Text books are generally poorly set out (they are often very busy and/or illogical) and fail to offer enough practice of particular grammar points at the appropriate level before becoming too difficult for many students.
The value of languages beyond learning a specific language is rarely, if ever, made clear, and neither are the language-based careers they can lead to, so it's no wonder students don't see the point.