Basically, you are disrupting your entire site. What ever search performance you had will be gone and will have to be rebuilt from scratch. Without creating 301 redirects at all, here is what will happen.
The pages that no longer exist, will return 404 errors and will for as long as there are links to the pages that no longer exist. Google will retry these pages for a period before giving up. Occasionally, Google will retry the again because links to these deleted pages remain. That is the way things are supposed to work. Do not use Search Console and Mark any correct 404 error as Fixed.
Google will find your new pages from your home page. It is like starting over. All new pages will have to rank just like any other new page. It will take time. Once Google has visited enough pages, sees a series of 404 errors, and sees a number of new pages, it will likely reindex your site fairly aggressively. This is normal.
Every new page will require time to properly index, gain performance metrics, and build links. If you are changing your entire site, the sites performance will suffer for quite a while. For this, You will want to promote your site. However, more importantly, for any old page that is important, if there is a relevant page, you should create 301 redirects even if it is just a few per day. Do this for any page that you consider to be highly valuable. That way you will redeem previously existing value. But do not go too slow on this. You do not have to redirect each page, just the ones that will help you retain your most important links and content.
Lastly, while it is mostly not necessary, it may help to create a sitemap if that is a simple process for you to do. If not, then do not worry about it. Submit your sitemap using Search Console. While Google should be able to crawl most any site without issue, the sitemap will help Google to audit your sitemap against what pages it can find. Ignore the metrics that Search Console gives you regarding pages indexed from your sitemap. Most of the time, this is hugely misleading. Do yourself a favor and only worry about whether Google can see your sitemap okay. After that, don't look. Do not resubmit your sitemap. Google will see it is updated and read it when it cares. Leave it alone. Just update your sitemap when you update your site.