What it (or rather, I) struggle with is single word translations. Instead of coming up with a number of options, it'll just give you one possible translation—the obvious one that you weren't looking for. On desktop you can then click on the word but those suggestions are.... let's say AI-like. Not necessarily wrong, but not like a proper enumeration of options like you'd get from a translation dictionary. I then try to give it context, but still it sometimes just insists on giving you the word you don't want and you need to look for a different translator. (For German–English there is dict.cc, but for Dutch or other languages I often end up doing a regular web search.)
This being said Google Translation got much better recently.
Note that if you want to see DeepL in use with a variety of languages, you can check the /r/europe subreddit. It's commonly used to translate national language articles into English.
I use it whenever I need to write any long-form English->Swedish - it simply cuts out the labor of thinking about grammar and spelling, and even handles idiomatic phrases perfectly. Also works perfectly in the other direction.
Also great with English->Spanish and the reverse.
I even used it to translate some official documents from Spanish into both English and Swedish for the tax authorities in both countries - no-one thought the translated documents seemed unprofessional, in any way, or questioned any of the complex legal terminology.
I barely try Google translate anymore. A couple of times when I've thought the DeepL translation was slightly 'off', I've tried Google and the result is usually comical garbage.
DeepL did a great job. It dealt with slang, informal grammar, and sudden shifts between formal and informal writing. It made some mistakes, but most of the jokes were still funny.
Google Translate produced near-incoherent gibberish for tougher passages.
DeepL was genuinely good for English/French. I can't speak to other language pairs.