Like a lot of you I have mostly worked in back-end or systems software. My CSS/UI/UX skills are very minimal. I get disheartened by how my project looks or don't start the project because I fear it would look crap or I despise doing the UI/UX work.
How do I solve this?
I'll prob. be downvoted but here's my honest opinion: I think you'll gain a lot career-wise to learn about UX and UI. You'll be able to understand products in a deeper level from the customer's side and will then be able to make better decisions as an engineer. You'll also have a much easier time working with designers and PMs. And, of course, your projects will feel and look great.
IMHO, the biggest bang for the buck you could learn is:
Reading material design from Google https://material.io is a great start. You may not like the UI of it, but the UX and explanations of why things are this way are really interesting.